About the pagination of this eBook

Due to the unique page numbering scheme of this book, the

electronic pagination of the eBook does not match the pagination

of the printed version. To navigate the text, please use the

electronic Table of Contents that appears alongside the eBook or

the Search function.

For citation purposes, use the page numbers that appear in the text.

Encyclopædia Britannica, Inc.

Chicago ■ London ■ New Delhi ■ Paris ■ Seoul ■ Sydney ■ Taipei ■ Tokyo

Britannica Illustrated Science LibraryBritannica Illustrated Science Library

INVERTEBRATESINVERTEBRATES

© 2008 Editorial Sol 90All rights reserved.

Idea and Concept of This Work: Editorial Sol 90

Project Management: Fabián Cassan

Photo Credits: Corbis, ESA, Getty Images, Graphic News,NASA, National Geographic, Science Photo Library

Illustrators: Guido Arroyo, Pablo Aschei, Gustavo J. Caironi,Hernán Cañellas, Leonardo César, José Luis Corsetti, VaninaFarías, Manrique Fernández Buente, Joana Garrido, CelinaHilbert, Jorge Ivanovich, Isidro López, Diego Martín, JorgeMartínez, Marco Menco, Marcelo Morán, Ala de Mosca, DiegoMourelos, Eduardo Pérez, Javier Pérez, Ariel Piroyansky,Fernando Ramallo, Ariel Roldán, Marcel Socías, Néstor Taylor,Trebol Animation, Juan Venegas, Constanza Vicco, CoraliaVignau, Gustavo Yamin, 3DN, 3DOM studio

Composition and Pre-press Services: Editorial Sol 90Translation Services and Index: Publication Services, Inc.

Portions © 2008 Encyclopædia Britannica, Inc.Encyclopædia Britannica, Britannica, and the thistle logo areregistered trademarks of Encyclopædia Britannica, Inc.

Britannica Illustrated Science Library Staff

EditorialMichael Levy, Executive Editor, Core EditorialJohn Rafferty, Associate Editor, Earth SciencesWilliam L. Hosch, Associate Editor, Mathematics and

ComputersKara Rogers, Associate Editor, Life SciencesRob Curley, Senior Editor, Science and TechnologyDavid Hayes, Special Projects Editor

Art and CompositionSteven N. Kapusta, DirectorCarol A. Gaines, Composition SupervisorChristine McCabe, Senior Illustrator

Media AcquisitionKathy Nakamura, Manager

Copy DepartmentSylvia Wallace, DirectorJulian Ronning, Supervisor

Information Management and RetrievalSheila Vasich, Information Architect

Production ControlMarilyn L. Barton

ManufacturingKim Gerber, Director

Britannica IllustratedScience LibraryBritannica IllustratedScience Library

Encyclopædia Britannica, Inc.

Jacob E. Safra, Chairman of the Board

Jorge Aguilar-Cauz, President

Michael Ross, Senior Vice President, Corporate Development

Dale H. Hoiberg, Senior Vice President and Editor

Marsha Mackenzie, Director of Production

International Standard Book Number (set): 978-1-59339-797-5

International Standard Book Number (volume):

Britannica Illustrated Science Library: Invertebrates 2008

Printed in China

www.britannica.com

978-1-59339-804-0

Invertebrates

Contents

Page 6

Origin andhabitatsPage 6

Crustaceansand arachnidsPage 34

Relationshipwith humansPage 80

The simplestlife-formsPage 18

Insects

Page 52

Bees are among the most importantinsects. They process the nectar offlowers to produce honey, a sugary

liquid that humans use as a sweetenerand nutrient. The nutritive component ofhoney is pure carbohydrate in the form ofsimple sugars, which are directlyabsorbed by the body. This characteristicgives honey its punch as a quick energysource. Edible in its natural state, it canalso be used as an ingredient of dessertsor to sweeten drinks. Not only bees,however, but also wasps play afundamental role in the lives of all livingbeings. Many plants depend on them forpollination of their flowers. Withoutthese insects there would be fewer fruitsand vegetables to eat.

Here we show you the inside workingsof a beehive. Did you know that onedifference between bees and other

insects is the organized communities thatbees form? Keeping in mind that eachartificial honeycomb has about 30,000inhabitants, there must be a way to keeporder, and the bees know by instinct howto do this. The queen, the drones, and theworkers know their roles and duties well.They may even die defending the colony,just like ants, who are also true masters oforder and productivity. Noteworthy in theworld of insects is their high degree ofevolutionary development. They are thehighest achievers of the animal world. Theylive all over the planet, need little food tosurvive, and escape from predators withhighly developed means of locomotion. All

ARTIFICIAL BEEHIVEMovable frames allow thebeekeeper to remove honeyand wax from each comb.

insects have jointed legs and an externalskeleton for protection. In this book youwill also be able to admire the beauty ofbutterflies and the changes theyexperience throughout their lives, and youwill discover the world through the eyes ofa fly. Have you heard that, among the35,000 known species of spiders, only 30are truly poisonous, and that without thesepoisonous creatures we would beswimming in a sea of insects? Alsointeresting are the many kinds ofspiderwebs that spiders use for makingtraps, mating, moving about, and coveringtheir burrows.

We invite you to explore the pagesof this fact-filled book, withfascinating photos and intriguing

facts about the inner and external lives ofthe invertebrates that share our world.Mosquitoes, for example, can pierce theskin of mammals and feed on their blood,and flies can eat solid food because theirdigestive process begins outside theirbodies. No athlete can jump like the flea, atiny, wingless insect that lives on the bloodof birds and mammals. We will also tell youabout beneficial insects that can be usefulto have in your house, and about others thatit would be better to control and keep away,because they can transmit sicknesses suchas Chagas disease. Just turn the page tofind detailed accounts along with carefullyselected images that will show you in fulldetail how some of the smallest creatureson Earth live, change, grow, andcommunicate. It is well worth it!

Invertebrates were the first forms ofanimal life on Earth. They are themost ancient and most numerous of

known life-forms. Some, such as worms,sea anemones, and jellyfish, are soft-bodied. Others, such as insects andcrustaceans, are hard-bodied. Some,including jellyfish, live in the water andswim freely. However, others, such ascorals and anemones, are fixed in oneplace. This fascinating world of tinycreatures has over 1.5 million knownspecies, with a wide variety of shapes and habits.

Tiny Creatures

LIFE BEGAN IN THE SEA 14-15

TEEMING FRESHWATER

ENVIRONMENTS 16-17

Origin and Habitats

The first life-forms appeared nearly4 billion years ago. The maingroups of organisms with complexcells (eukaryotes) evolved duringthe Precambrian Period. Fossils

found in Australia and Canada show thatthose invertebrates had soft bodies, quitedifferent from those that exist today.Members of the kingdom Animalia becameadapted to many environments, extending

from the bottom of the ocean to the highestmountain peaks. We will show you theoldest species and many of the main groupsof today: sponges (phylum Porifera); corals,anemones, and jellyfish (phylum Cnidaria);

shellfish (phylum Mollusca); sea worms andearthworms (phylum Annelida); insects,spiders, millipedes, and crustaceans(phylum Arthropoda); and starfish and seaurchins (phylum Echinodermata).

TRACES OF ANCIENT LIFE 8-9

FROZEN IN TIME 10-11

THE FIRST CONQUEST 12-13

ANOMALOCARISThe largest predator of trilobites inthe Cambrian Period, it measuredup to 20 inches (0.5 m) long.

INVERTEBRATES 9

EVOLUTIONTrilobites are the best-known fossilized animals to appearduring the Cambrian explosion. The fossil record shows anextraordinary proliferation of life-forms during this stage of life on Earth. From this time on, no new structures ofmorphological organization appeared. Rather, existing forms evolved and diversified.

FOSSILS Fossils yield clues about life inthe past. By comparing fossilizedorganisms from different periodsof the Earth's history withorganisms of today, we candeduce how various life-formshave changed over time.

SIZESThe Burgess Shaleinvertebrates had a wide rangeof sizes, from microscopic tonearly 7 feet (2 m) long. (Dogs,on the other hand, have anarrower size range; the mostcommon breeds range from 20to 40 inches [50-100 cm] tall.).

CANADALatitude 51° 25’ 30” NLongitude 116° 30’ 00” W

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Mouth

Anomalocaris

Mouth

600 million yearsAGE OF THE FIRST SPECIMENS FOUND

540 million yearsAGE OF THE FOSSILS FOUND IN THIS BED

This fossil bed isoutstanding for the variety ofcreatures found.

AUSTRALIALatitude 35° 15’ SLongitude 149° 28’ E

The first specimenswere found in theEdiacara Hills.

20 inches(50 cm)

Millions of years ago, our planet was not as we know it today.The continents were arranged differently, and the climate, flora,and fauna were different. How do we know this? We have

learned these things by finding and studying fossils, remains of past life-forms that are preserved in both geography and time. The Ediacara, insouthern Australia, and the Burgess Shale, in Canada, are two regionswith extensive fossil beds of soft-bodied invertebrates. Both areas haveshed light on what is known as the Cambrian explosion.

WIWAXIAA rare marvel with noknown biologicalrelationship to anyother life-form.

ANOMALOCARIS20 inches (50 cm) long.

CANADIAEstimated to havebeen between 0.8and 2.0 inches (2-5 cm) long.

CHANCELLORIAThis cylindrical formis thought to havepossibly been asponge.

OTTOIAThis priapulidworm couldmeasure up to3 inches (8 cm) long.

MARRELLA SPLENDENSLess than one inch long,this creature is thought tolive on the seafloor.

JELLYFISHEdiacaran

CHARNIAOne of the mostwidely found fossilsof the EdiacaranPeriod. It is believedto have been relatedto certain cnidariancolonies.

DICKINSONIA SPECIESBelieved to belong to the Cnidarian(coral, jellyfish, anemones) orAnnelid (worms) phyla. The largestwas 17 inches (43 cm) long.

Olenoides Xandarella Emeraldella Yohoia Sidneyia Burgessia

Dog

EdiacaraThis group, called Ediacara fauna, is the oldest knowngroup of multicelled organisms. Found in Precambrian

rock, it predates the great Cambrian explosion. Its age is around600 million years; it contains impressions, or molds, of diverseanimal forms conserved in sedimentary rock, without a trace ofhard parts. The first such bed was found in southern Australia,in the Ediacara Hills.

Burgess ShaleLocated in Canada, Burgess Shale iswell known for its fossil bed of soft-

bodied animals from the Cambrian Period.This bed gives a glimpse of what ocean lifewas like during the Cambrian Period, withspecimens of the four main types ofarthropods: trilobites, crustaceans,horseshoe crabs, and Uniramia (the group that includes insects).

8 ORIGIN AND HABITATS

AYSHEAIAFrom 0.5 to 2.5 inches (1-6 cm) long.

OPABINIAFrom 1.5 to 3 inches (4-7 cm) long.

Traces of Ancient Life

10 ORIGIN AND HABITATS

Frozen in TimeF

ossils give evidence about many different ancient life-forms. Bones, footprints, and other signs ofanimal and plant life can become fossils as

their organic components are replaced bymineral compounds. Many arthropods weretrapped in the sap of certain trees. Whenthis sticky substance hardened, itbecame what is called amber.Amber is very useful for studyingprocesses that gave rise to thediversity of life on Earth.

INVERTEBRATES 11

Properties and CharacteristicsAmber is a material derived from the fossilized resin ofcertain trees that lived between 144 and 65 million years

ago. Over time they were fossilized, forming large, irregularmasses within layers of sandstone and slate mixed with clay.Masses of amber range from very small, only a fraction of aninch, to many times longer, up to 20 inches (50 cm) in length,with a hardness of 2 to 3 on the Mohs scale. Amber is composedof carbon, oxygen, and hydrogen.

During the Cretaceousand Tertiary Periods,forests covered a widearea. The trees secreteda resinous substancethat oozed out in theform of drops.

The resin insulated the animalfrom the atmosphere andprotected its remains fromwater and air. As the resinhardened, it gradually formed aprotective, pressure-resistantlayer. Over time this layer wastransformed into what weknow today as amber.

Diverse OriginsThe color of fossilized amber depends on the type of tree itcame from, when it was formed, and the environment

where it was fossilized. Amber is usually yellow, although it maycome in many shades ranging from orange, red, brown, blue, andgreen to transparent varieties. Although color is important,amber is classified according to its origin.

FOSSIL IN AMBERPhotograph of amber thatcontains fossil remains from 38million years ago. This piece isvalued at nearly $35,000.

FOSSILIZED ARACHNIDThis spider, perfectly conservedthanks to the protection of theamber, enables scientists to makereliable comparisons with generaand species of today.

The melting point of amber

572° F(300° C)

1

2

3Mineral deposit Origin Shades

Baltic Eocene conifers

Burma Eocene Burseraceans

Dominican Republic Miocene legumes

Sicily Miocene Burseraceans

Romania Miocene legumes

Mexico Miocene legumes

Canada Cretaceous conifers

Ancient Life-FormsFinding these fossilized creatures enables us to learnabout life-forms and environments of the past. The

presence of certain fossils can help us to determine what theclimate was like millions of years ago and to date rock layers.We know that certain plants and animals lived in specificperiods. Their presence or absence can help us determine theage of the rock layer where they are found. Not only did amberpreserve plants and animals, but it also trapped air bubbles.

Amber containing animals thatlived millions of years ago isused to make jewelry. Its pricedepends on the type oforganism it contains.

Value

This substance accumulated on tree branches and bark and at thefoot of the trunk, trapping allsorts of plants and animals(even toads) that got stuckin the thick resin.

The First Conquest

12 ORIGIN AND HABITATS INVERTEBRATES 13

The Most SuccessfulBeetles (order Coleoptera) are the most prolificand diverse group of the animal kingdom. This ismostly because of their chitinous exoskeletonsand highly compact elytras (wing covers), whichgive each species the hardness, flexibility, texture,or color it needs to adapt to its environment.

To be able to live on land, invertebratesdeveloped ways of breathing andmoving that were adapted to a

land environment. Thus insects, whichcan walk and fly, have populated landand air environments. Other invertebrateshave also become accustomed to life inthis element, and they play an importantrole in land ecosystems.

Who EatsWhom?The relationships of eatingand being eaten that areestablished among theorganisms of anecosystem are called thefood chain. In contrast toplants, whose capacity forphotosynthesis gives them the roleof food producers, invertebratesoccupy various levels in the foodchain as food consumers.

Small ArthropodsMost land- and air-dwelling arthropods have atracheal respiratory system consisting of highlyefficient air tubes that supply oxygen directly tothe cells and tissues. The tracheal system makes itpossible for these arthropods to maintain a highmetabolic rate, but it also tends to limit body size.That is why land-dwelling arthropods are relativelysmall compared to the rest of the animal kingdom.

NaturallyProgrammedThe world of air- and land-dwellinginvertebrates includes societies, such as thoseof bees, wasps, and ants (order Hymenoptera).The bees' dances to inform other bees aboutthe location of new food sources, their strictdivision of labor, or the structure of aspiderweb correspond to patterns of behaviorspecific to each species. Each individual carriesthese patterns inscribed within, like acomputer program that executes perfectly.

OVER

350,000SPECIES OF BEETLES

ARE KNOWN.

WASPPolistes sp.

CENTIPEDELithobius sp.

EARTHWORMLumbricus sp.

SPIDERDrassodes sp.

BURYING BEETLENicrophorusinvestigator

BLACK VINEWEEVILOtiorhynchussulcatus

CLICK BEETLEAgriotes lineatus

PILLBUGSArmadillium sp.

DESERT MILLIPEDEOrthoporus ornatus

TICKBoophilus sp.

SILVERFISHLepisma saccharina

BLOOD-RED ANT(WORKER)Formica sanguinea

SILKWORMBombyx mori

CRAMER'S BLUE MORPHOMorpho rhetenor

FIRST LEVELInvertebratesthat eat plants

1 SECOND LEVELCarnivores thateat herbivorousinvertebrates

2 THIRD LEVELLarger invertebrates thateat other carnivorousinvertebrates

3

THE ORDER OF THE FOOD CHAIN

LadybugsFleas

Spiders

70%OF THE SPECIES THAT

LIVE IN TREES AREINSECTS.

ASIAN TIGERMOSQUITOAedes albopictus

PRAYING MANTISFamily Mantidae

BROWN GARDEN SNAILHelix aspersa

EUROPEAN HORNETVespa crabro

COMMONFURNITURE BEETLEAnobium punctatum

Tunnels boredby beetles

FEEDING ON DEAD MATTER

MONARCHBUTTERFLYDanausplexippus

Life Began in the Sea

14 ORIGIN AND HABITATS INVERTEBRATES 15

Invertebrates are not defined by any single commoncharacteristic, but simply by not being vertebrates. Theirheterogeneity is most notable in the ocean. Some 3.8

billion years ago, life arose in our planet's oceans. The speciesthat inhabit the ocean waters show greater diversity than

50,000KNOWN CRUSTACEAN SPECIES

THE VAST MAJORITY LIVE IN THE SEA

WHITE JELLYFISHRhizostoma pulmo

RADIANT SEA URCHINAstropyga radiataDefends the crab against predators

URCHIN CRABDorippe frasconeTransports the sea urchinin a form of symbiosis

COMMON OCTOPUSOctopus vulgarisFound up to 30 feet (10 m) deep

CHRISTMASTREE WORMSpirobranchus giganteus

SEA CUCUMBERThelenota sp.

SPONGESpongia officinalisAbsorbs nutrientsfrom the water

BROADCLUBCUTTLEFISHSepia latimanus

BEADLET ANEMONEActinia equina

CORALAcropora sp.Coral reefs areenvironments inhabitedby thousands of oceancreatures. They make uptheir own ecosystem.

JELLYFISHThysanostomaloriferum

those found in other environments. Some forms of animallife, such as corals and sponges, are so simple that theyare not able to move about on their own. Others,such as some cephalopods, show greatintelligence and skill.

RADIAL SYMMETRY

ANTARCTICKRILLEuphausiasuperba

BIGFIN REEF SQUIDSepioteuthis lessonianaMale and female

AMERICAN LOBSTERHomarus americanus

CARAMOTEPRAWNPenaeuskerathurus

RED STARFISHEchinaster sepositus

SEA SLUGChromodoriswillani

TIGER COWRYCypraea tigris

COMMON STARFISHAsterias rubens

OYSTERSCrassostrea sp.

A World Without InsectsArthropods are the most prolific animals on theplanet. But just as insects (hexapods) reign on land,crustaceans have been successful in the water.They breathe through gills, and some, such as krill,are microscopic. Most, however, are larger thaninsects-mostly because they have no need ofcomplex and costly metamorphosis.

Unique ShapesSome sea organisms, such as jellyfish, some sponges, andanemones, are very simple. Others, such as sea urchins andstarfish (phylum Echinodermata), are more complex. However, allof these life-forms have a body plan called radial symmetry,which, in contrast to bilateral symmetry, is found only in the sea.

The LargestThe reduced effects of gravity in the waterenable the largest invertebrates to live inthe sea. Out of the water, octopus andsquid-cephalopod mollusks with no rigidstructure or joints in their bodies-would notbe able to move or hold themselves up, letalone hunt. Perhaps this is why noinvertebrates of this size are found on land.

Medium and SubstanceGills enable oxygen from the water to enter directly intoan animal's circulatory system. Through tiny chambers,they exchange gases with the surrounding water. But thesimplest organisms, without digestive tracts, feed by

absorbing other substances and traceelements from the water.

66 feet (20 m) length

of the giant squidArchiteuthis dux

Teeming Freshwater Environments

16 ORIGIN AND HABITATS INVERTEBRATES 17

8% OF INSECTS LIVEIN WATER

Adapted to the WaterSome water species breathe throughair tubes or tracheae. All suchorganisms had to develop amechanism or device for providingthemselves with air, becausetracheae and tracheoles are uselessfor breathing underwater.

means they must obtain a reserve of air or come to the surface tobreathe. Crustaceans have mechanisms that protect them fromlosing salt in fresh water. With these adaptations, invertebrates makeseemingly calm waters the scene of an intense struggle to survive.

GREAT DIVINGBEETLEDytiscusmarginalis

LIFE CYCLE OF THECOMMON MOSQUITO

DIVING BELLSPIDERArgyronetaaquatica

On the BorderThe areas in and around water andclose to the water's surface are thescenes of a battle for survival. Mostfreshwater insects live in this zone.

DRAGONFLY NYMPH

In Fresh WaterOcean invertebrates live in an osmotic balancebetween water and the salts the watercontains. Invertebrates that live in estuaries orother places where salt water receives currentsof fresh water (euryhaline organisms) mustkeep the concentration of salts in their bodiesconstant, even when the salinity of the waterchanges. In fresh water, with its lowconcentration of salts, crustaceans developedmechanisms to eliminate water and capturesalts actively-that is, their bodies expendenergy on these functions. For this reason rivercrustaceans, unlike sea crustaceans, urinate.

WHITE-CLAWED CRAYFISHAustropotamobius pallipesGlands on its antennae excretewater and maintain thebalance of salts in its body.

WATER BOATMAN(BACK SWIMMER)

Notonecta glauca

One Species, Two EnvironmentsMany species of land- and air-dwellinginsects lay their eggs in water. Afterhatching, the larvae undergometamorphosis in the water. This facthas enabled certain species to prosperby colonizing more than oneenvironment at once. Not only doesthe same individual inhabit differentenvironments at different stages ofits life, but it also has distinct feedinghabits and means of breathing duringthose stages. That fact keeps adultsof the species from competing with the young for food.

LARVAEAfter one week, the eggs hatchand the larvae are born.

2

PUPAEThe larva moltsfour times as itgrows, finallyreaching thepupa stage.

3

ADULTAfter a few days thepupa's skin splitsand the adultmosquito emerges.The adult willlive for onlya fewweeks.

4

EGGSAfter feeding onblood, adult femaleslay 40 to 400 eggson the surface ofthe water.

1

Living Off OthersSome organisms are parasites. They do not obtaintheir own food; rather, they live at the expense ofanother species. Although they depend on anotheranimal for sustenance, they avoid doing the otherspecies too much harm. Otherwise, the parasitewould have to find a new host.

BLOOD-FLUKES(BILHARZIA)Schistosoma sp.

TRICHODINATrichodina fultoni

MEDICINAL LEECHHirudo medicinalis

COPEPODCyclops sp.

ZOOPLANKTON

GREAT PONDSNAILLymnaeastagnalis

COMMON POND SKATERGerris lacustrisLives in water. It has just theright weight and structure totake advantage of surfacetension when the water is calm.

EMPEROR DRAGONFLYAnax imperatorThe adults feed on small

flying insects that livenear plants by the

shore of bodies offresh water.

Moltingdragonfly

In rivers, ponds, lakes, lagoons, and swamps, manyinvertebrate species are adapted to life in the water butcome from other habitats. Thus, water beetles breathe,

not with gills, but with spiracles, the way land insects do. This

MAYFLYHexagenia sp.

WATER MEASURERHydrometra stagnorum

CADDISFLY LARVALimnephilus sp.

WATER BEETLELARVA

THE PROCESSLASTS ABOUTONE MONTH

Most parasiticworms aremicroscopic insize. The onesshown here arehighly magnified.

JOINTLESS 28-29

GENERATING ADDED VALUE 30-31

POWERFUL TENTACLES 32-33

The Simplest Life-Forms

Even though most organismssuch as sponges, jellyfish, andsea anemones look likevegetables, they belong to theanimal kingdom. Many of these

simple invertebrates are unable to movefrom one place to another; some evenlack certain tissues or an entirerespiratory or digestive system. Other,more developed species, such as squid

and octopus, can move about and havebecome skilled marine predators.Cephalopods are the most highly evolvedmollusks. Their heads have highlydeveloped eyes, a mouth with two

horn-like jaws, and tentacles withsuckers to trap their prey. Somecephalopods live in deep-sea waters,whereas others stay close to shore.

RADIAL SYMMETRY 20-21

SEA CARNIVAL 22-23

AQUATIC 24-25

LEGLESS 26-27

THE SIMPLICITY OF THE JELLYFISHThe jellyfish is a very simple animal with agelatinous consistency and with no respiratory,digestive, or excretory systems. It drifts aroundin warm ocean waters.

EchinodermsThis phylum includes sea lilies, seacucumbers, urchins, and starfish. Theechinoderms have an internal skeletonmade of calcified plates and a locomotionsystem made up of ambulacral grooveswith rows of tube feet. In mostechinoderm species, theendoskeleton is made of tinycalcareous plates heldtogether by skin andmuscle tissue.

CnidariansCnidarians are a group of aquatic animals thatincludes jellyfish, hydras, sea anemones, andcorals. Their cells are organized in true tissues.They have specialized cells called cnidoblasts forstinging prey and for defense. Two basic types ofcnidarians are polyps and jellyfish.

PoriferaAre sessile aquatic animals. Most live at the bottom ofthe ocean, although there are some freshwater species.They are the simplest animals, lacking organs or truetissues, and their cells are independent to a certainextent. They are basically water-filtering bodies formedby one or more cavities. Most porifera have no definiteshape, but some have radial symmetry.

BLASTULAThe zygote, after a series of celldivisions, becomes ablastula, or hollowsphere, of cells.

3

Most commonhabitatCOASTS OF

THE UNITED STATES

SCYPHOZOA: Jellyfish

REPRODUCTION

FERTILIZATIONFertilization takesplace in thewaters near thejellyfish, resultingin a zygote.

2

GAMETESAdult jellyfishproduce sperm andegg cells duringmeiosis and thenrelease them.

1

PLANULAThe blastula lengthensand becomes a ciliatedlarva called a planula.

4

POLYPThe planula larva settles at the bottom, where itattaches to a surface.There it develops a mouthand tentacles, andtransforms into a polyp.

5

JELLYFISHThe polyp's bodygrows andbegins to formjellyfish, whichpile up like astack of plates.

6

Gastrovascularcavity

Mesoglea

Mouth

Epidermis

Gastrodermis

Oscula

The water withfood particlesenters throughthe porocytes.

Spicule

NucleusFlagellum

TYPES OF PORIFERA ACCORDINGTO ORGANIZATION

ASCON SYCON LEUCON

Direction ofwater flow

RADIALSYMMETRYThe body parts areorganized around acentral axis like thespokes on the wheelof a bicycle. Any planepassing through thebody will divide it intotwo halves, eachmirroring the other.

9,000SPECIES OF CNIDARIANS

(COELENTERATES).

STINGING CELLUsed for defense

NucleusCnidocyst

OperculumCnidocilium

Unfoldedstinging tube

INTACT1

DISCHARGING2

DISCHARGED3

Barb

Rolled-uptube

ECHINODERM CLASSES

ASTEROIDEAStarfish

ECHINOIDEASea urchins

CRINOIDEASea lilies

HOLOTHUROIDEASea cucumbers

OPHIUROIDEABrittle stars

ECHINODERMmeans that thisanimal's body iscovered by aspiny skin.

JELLYFISHPelagia noctiluca

Center

Imaginary axis

Epithelial cell

Watercoming out

CLASSIFICATION

THERE AREAPPROXIMATELY

ANTHOZOA: Seaanemones and corals

SEA URCHINStrongylocentrotus franciscanus

5,000SPECIES (150 ARE

FRESHWATER, AND THEREST ARE MARINE).

THERE AREAPPROXIMATELY

7,000LIVING SPECIES AND 13,000 EXTINCT SPECIES OF ECHINODERMS.

THERE ARE APPROXIMATELY

Youngjellyfish

Adultjellyfish

HYDROZOA:Asexual polyp

Many of the numerous invertebrates on Earth live in theocean. Some, such as polyps and jellyfish, have radialsymmetryΩthat is, their bodies are structured around an

axis. A typical echinoderm such as the starfish has tiny, flexible,tube-shaped legs arranged like the spokes of a wheel. The animaluses them to hold onto surfaces and to move. Sponges, on theother hand, are very simple, multiple-celled animals, withmany small pores that they use to feed.

Radial Symmetry

20 THE SIMPLEST LIFE-FORMS INVERTEBRATES 21

Coral ReefsCorals are small polyps withtentacles that grow at their

base throughout their life,generating a calcareous exoskeleton.This skeleton forms masses, orbranches. Most corals grow incolonies; the skeletons form hugecalcareous masses called reefs. Coralslive mostly in warm, shallow oceanwaters. Their reproduction can be bothsexual and asexual, by division or bygemmation. They feed on plankton.

Beautiful but DeadlyBeautiful for their shapes and colors thatvary even within the same species, and

dangerous for the poison they use to sting bothvictims and predators, sea anemones live inalmost all marine latitudes, and at varyingdepths. Tropical marine anemones can measureup to 3 feet (1 m). They have a basal disc, whichallows some species to attach to rocks, andothers to slither, and still others to penetratethe seafloor. They trap live prey, even fish, withthe many tentacles around their mouths.

TENTACLESWith stinging cells, to hunt and move

SEA ANEMONEAny vertical plane passingthrough its center dividesit into two equal parts.

MOUTH ORALDISC

INCOMPLETEMESENTERIUM

MESENTERIUMFILAMENT

RETRACTORMUSCLE

COMPLETEMESENTERIUM

SEPTALPERFORATION

GASTROVASCULARCAVITY

PHARYNX

BASAL DISC

HARD CORALSgrow over the surface of thelime-bearing substrate.

100 feet(30 m)

THE MOST COMMON DEPTH ATWHICH CORALS GROW

SOFT CORALSbranch out; their skeleton isnot lime-based but horn-likeand flexible.

CORALPOLYP

CLOWNFISHInexplicably, the sea anemone'spoison does not affect this species.

CONTRACTIONThe sea anemonereduces its size.

DISTENSIONBy means of theretractor muscle

EXTENSIONWhen the wateris calm

Tentacles

Column

Base

Waterflow

Gastric cavityDivided into severalcavities inhydropolyps

Mouth Through here theanimal ingests

its food and excretes wastes.

Tentacleswith stinging cells

Calciumcarbonate

Livetissue

Hard skeletonA mass that growsby the accumulationof dead polyps

Connecting tissueConnects one polypwith another

CORAL WALLSEven though some coral walls live alone,most form colonies that can growupward at up to 3 feet (1 m) every year.

9,000THE NUMBER OF CNIDARIAN

SPECIES IN THE WORLD

ADAPTATION OF SHAPETo avoid being swept away in the current, thesea anemone retracts on sensing a water flow.

Corals and anemones, together with jellyfish, make up thephylum Cnidaria. Some characteristics they share are theirbright colors, tentacles that secrete stinging substances, and a

digestive system with a common opening for ingestion and excretionΩthesimplest digestive system in the animal kingdom. All of these organismsare quite simple. Corals generally form colonies, large groups of smallpolyps that stay practically immobile and feed on microorganismsbrought to them by water currents. Sea anemones, on the other hand,are solitary and can trap prey despite their limited locomotion.

Sea Carnival

22 THE SIMPLEST LIFE-FORMS INVERTEBRATES 23

INVERTEBRATES 25

SuctionThe sac contracts and putspressure on the ambulacralgroove. The muscles tense andforce the water back into thesac, causing suction betweenthe groove and the surface withwhich it makes contact.

STARFISH Archaster typicus

SEA URCHINAstropyga radiata

Stages ofMovementThe ambulacral groove and tube feet allow thestarfish to perform the movements it needs forlocomotion. The feet are arranged in twoparallel lines along the arm, and the feet at theother end have a sensory function, monitoringthe substrate over which the creature moves.

Echinoderms (phylum Echinodermata) are one of the best-known groups of marine invertebrates. Sea urchins and starfish, despite theirapparent differences, are part of the same group and share characteristics

such as five-radial symmetry. This phylum has an aquatic vascular system withmany ambulacral grooves with tube feet, which it uses for locomotion,capturing prey, and breathing. In addition, it has an internal skeletonmade of calcareous plates. These creatures lack a brain or eyes,so they use photoreceptors to sense movement.

6,000

Closedvalve

SubstrateSucker

Sac

Ambulacral Grooves

570million yearsTHE LENGTH OF TIME ECHINODERMSHAVE BEEN IN EXISTENCE

SACFills with water,expands, and clingsto the surface

1

2

3

When the sac musclescontract, they force the liquidto pass to the ambulacralgroove, which lengthens andmakes contact with anadjacent surface, or substrate.

The muscles can make the tubefeet move to either side, and thecoordinated movement of all thefeet in one direction causes thestarfish to advance.

The area near the sucker secretesan adhesive substance that helpskeep it attached to the surface.The lateral muscles in the groovecontract, and the liquid returns tothe sac for locomotion.

Aquatic

SKINThe undersideis covered byspines.

RADIAL CANALThe water passes andcirculates to the sacs.

ESOPHAGUS

MOUTHSurrounds thefood and breaks itdown withstomach juices

STOMACH

PYLORIC CONDUITMoves the water thatends at the pyloric cecum,which functions as adigestive gland

BARBUsed fordefense

SPINESThere are two varieties ofspines: larger primaryspines and shortersecondary spines. They areusually cylindrical with anarrowed tip.

24 THE SIMPLEST LIFE-FORMS

These structures are hollowcylinders with thick walls

that straighten and move when astarfish injects water into certainvesicles in its body. The ambulacralgrooves end in suckers that theanimal uses to attach itself to

objects, enabling it to move atsurprising speed. These sensitivefeet shrink if touched abruptly,hiding behind a rim of rigid spines that protect them from harm.

Defense SystemCharacterized by complete five-sidedsymmetry, sea urchins' bodies are covered

by several mobile spines that give them adangerous appearance. The spines are spreadevenly throughout the skeleton's surface andare used as a defense system.

THE NUMBER OFECHINODERM SPECIES

INVERTEBRATES 27

ENDODERM

MESODERM

COELOM

ECTODERM

DIGESTIVECAVITY

Mouth

Anus

Pharynx

Intestine

Clitellum

Hearts

Segmentedbody

Flatbody

Round body

AT LEAST

100,000KNOWN WORM SPECIES

Reproductivesystem

1 2 3

Movement Guided by LightFlatworms have eyespots, or light-sensitive eyes, on the front end of their bodies. When exposed to excessive light, the eyeswithdraw and remain immobile.

Tissuesare formed in layers and are based on thepresence of internal cavities. This annelid hasthree layers and one cavity, the coelom, whichcarries fluids through the body like ahydraulic skeleton.

ReproductionFlatworms and annelids areusually hermaphrodites;nematodes usually have separatesexes. In some cases the wormsplits into two, resulting in twonew worms.

Digestive SystemIn annelid worms, the digestive system extends in a straightline from the oral opening to the anus. It includes the mouth,muscular pharynx, esophagus, crop, gizzard, and intestine.

Classes of Worms

PLATYHELMINTHES ANNELIDANEMATODA

LOCOMOTIONSnake-like undulations along thedorsal-ventral plane

Worms are invertebrates with long, soft bodies and no legs. They areclassified into three phyla. Flatworms are the simplest type; most areparasites, although some are free-living. Nematodes have a

cylindrical body with a hard outer surface. Segmented worms are morecomplex; they include leeches, earthworms, and sea worms. Many specieshave an impact on plants, animals, and humans.

WORM Nematode enoplida

EARTHWORMLumbricus terrestris

28 feet(8.5 m)LENGTH OF THE LONGESTWORM: PLACENTONEMAGIGANTISSIMUM

Legless

LEMNISCIFood storage

NECKRetracts and remains hidden

TISSUEFibrous andelastic

HOOKSHold the wormin place

SetaeSetae are bristle-likestructures.

Segments

FOODBacteria andorganic wastes

26 THE SIMPLEST LIFE-FORMS

EPIDERMIS

PROBOSCISPartly foldedinward

SPINESPierce the wall ofthe host

28 THE SIMPLEST LIFE-FORMS

JointlessT

he body of most mollusks is soft, extremely flexible, and without joints,yet has a large and very hard shell. Most mollusks live in the ocean,but they are also found in lakes and land environments.

All modern mollusks have bilateral symmetry,one cephalopod foot with sensory organsand locomotion, a visceral mass, and acovering, called the mantel, thatsecretes the shell. Mollusks alsohave a very peculiar mouthstructure called a radula.

INVERTEBRATES 29

GastropodsThese mollusks are characterized bytheir large ventral foot, whose wave-like motions are used to move fromplace to place. The group comprisessnails and slugs, and they can live onland, in the ocean, and in fresh water.When these animals have a shell, it is asingle spiral-shaped piece, and the extremeflexibility of the rest of the body allows thegastropod to draw itself up completely withinthe shell. Gastropods have eyes and one or twopairs of tentacles on their head.

PROSOBRANCHIAThis mollusk subclass mainly includesmarine animals. Some have mother-of-pearlon the inside of their shell, whereas othershave a substance similar to porcelain.

OPISTHOBRANCHIAare sea slugs, which arecharacterized by having avery small shell or noshell at all.

Nervoussystem

Gills

Digestivetract

RADULA

CephalopodsCuttlefish, octopus, squid, and nautilus are calledcephalopods because their extremities, ortentacles, are attached directly to their heads.These predators are adapted to life in theoceans, and they have quite complex nervous,sensory, and motion systems. Their tentaclessurround their mouths, which have a radula anda powerful beak. Cephalopods can be 0.4 inch (1cm) long to several yards long.

COLEOIDEACephalopods of this class have a verysmall internal shell, or none at all, andonly two gills. Except for the nautilus,this class includes all cephalopods alivetodayΩoctopus, cuttlefish, and squid.

THE NUMBER OF LIVINGMOLLUSK SPECIES; AS

MANY MORE HAVEBECOME EXTINCT

100,000

BivalvesMollusks with a shell divided into two halves.The two parts of the shell are joined by anelastic ligament that opens the shell, adductormuscles that close the shell, and the umbo, asystem of ridges that helps the shell shuttogether. Almost all bivalves feed onmicroorganisms. Some bury themselves in thewet sand, digging small tunnels that let inwater and food. The tunnels can be from afraction of an inch long to over a yard long.

LAMELLIBRANCHIATAinclude most bivalves.They use gills tobreathe and to feed.They have nodifferentiated head,eyes, or extremities.They can grow up to5 inches (13 cm) long,and they rest on theocean floor.

PROTOBRANCHIAThis class includes bivalves with asplit lower foot, called a sole.Bivalves use their gills only tobreathe. This subclass includes smallbivalves 0.5 inch (13 mm) wide,called nutclams (Nucula nitidosa).

Under the SandMany mollusks live buried under the sandin order to hide from predators and theeffects of waves, wind, and suddenchanges in temperature.

LUNGEDSnails, land slugs, andfreshwater slugs havelungs, and their lung sacsallow them to breatheoxygen in the atmosphere.

NAUTILOIDEAThis subclass populated the oceans of the Paleozoic and Mesozoicperiods, but today only one genusΩNautilusΩsurvives. A nautilus has anouter shell, four gills, and tententacles. Its shell ismade from calcium, isspiral in shape, and isdivided intochambers.

BENDING OF THE SNAILIn snails, bending is a veryspecial phenomenon that movesthe cavity of the mantle from therear toward the front of thebody. The visceral organs rotate180 degrees, and the digestivetube and the nervous connectionscross in a figure eight.

LUNG

SEA ANGELCandida sp.

GONADKIDNEY

DIGESTIVEGLAND

INTESTINE

SALIVARYGLAND

ESOPHAGUS

FEMALESEXUAL ORGAN

BROWN GARDEN SNAILHelix aspersa

GREEN MUSSEL Perna viridis

NAUTILUSNautilus sp.

COMMONCUTTLEFISHSepia officinalis

SCALLOP Pecten jacobaeus

Razor clam

Ottershell

TellinCockle

HEART

COMMONEUROPEANOYSTEROstrea edulis

CULTUREDPEARLS

NATURALPEARL

Pearl FormationOccasionally grains of sand or parasites accidentally becomelodged in an oyster's body and cannot escape. To relieve theannoyance, the oyster begins a defensive action and secretes asmooth, hard, crystalline substance called nacre around theobject. Cultured pearls are formed from particles that areintentionally inserted into an oyster.

Types of pearls

INNER SURFACE OF THE SHELLSensory tentaclesenable the oyster todetect light anddarkness.

SHELLComposed of twopieces or valves

INCUBATIONPearl cultivation began inJapan. It consists of insertinginto the body of a live oystera small, round particle madefrom the shell of a freshwaterbivalve. The oyster secretesmother-of-pearl substancesfrom a gland in its liver tocover the object, and thepearl begins to grow.

MANTLE FOLDsurrounds the mantle andcontrols the flow of water.

PALPSselect thefood.

GILLSabsorb oxygenfrom the water.

FOOTSeldom used; theoyster prefers to swimrather than dig.

HINGE LIGAMENTjoins the two valvesat their upper part.

DIGESTIVE GLANDIts cells absorb anddigest food particles. PEARL

Surroundedby nacre

OYSTERSRough

CLAMSPrickly

MUSSELSSmooth

INVERTEBRATES 31

TENTACLEShave sensoryorgans.

MUSCLEA fiber keeps theshell closed.

1

HARVESTCultured pearls make up 95 percent of thepearls currently sold. About 500 millionpearls are produced every year. However,pearl farming is a demanding and difficultbusiness because of the nature of pearloysters: out of 100 oysters cultivated, only30 will be harvested.

3

New, uniform layers are constantlyadded to the pearl, and the cultivatorleaves the pearl in place until it reachesthe required diameter and quality.During the process, humans interveneonly to provide the oysters in farmswith the right temperature, watercurrents, and cleanliness to favor thegrowth of pearls.

GROWTH OF THE PEARL

2

Bivalves are sought after and cultivated for their pearls. Pearls are said to be thequeen of gems, because they were discovered over 4,000 years ago and wereused as important symbols in many ancient cultures. In spite of their

high price, pearls start out as a nuisance for the animal that creates them,which could be an oyster, a clam, or a mussel. Oysters produce themost valuable pearls, which are noted for their luster.

3 to 8yearsTIME IT TAKESFOR A PEARLTO GROW

2%OF THE HARVEST WILLYIELD PERFECT PEARLS.

LAYERS OF NACREON THE PEARL

LAYERS OF NACRE ON THE SHELL

Oysters Tied with ropes

Grain of sand

Tongue

Introduction offoreign body

A

The oystersecretesnacre tocover it.

B

Organic layer

30 THE SIMPLEST LIFE-FORMS

HANGING OYSTERSThese oysters aresuspended frombamboo rafts inareas withabundant plankton.

PearlProducers

They can be roundor elongated like agrain of rice.

The number of pearl cultivatorsis estimated at nearly 5,000.Japan is the main producer.

Aragonite crystal

Generating Added Value

32 THE SIMPLEST LIFE-FORMS

Powerful TentaclesT

he eight-tentacled octopus is one of the few large ocean cephalopodsto live in deep water. It is usually found on the rocky or sandybottoms of shallow waters near the mouths of rivers. It generally

moves slowly, sometimes moving in brief spurts, but it can reachgreat speeds when hunting or fleeing. Some are quiteintelligent, having highly evolved brains. The ring-shaped muscles

relax, and the long musclescontract. Water enters.

When the ring-shapedmuscles contract, they expela jet of water that propelsthe octopus backward.

BREATHING

PROPULSIONH2O

relaxedmuscle

contractedmuscle

chitinousring

Gill

1

SUCTION

1

2

2

Head

Funnel

AttackTo attack, the octopus points its funnel in thedirection opposite to its motion. The common octopus

(Octopus vulgaris), a species that can grow up to 40 inches(1 m) long and inhabits the Mediterranean Sea and NorthAtlantic Ocean, moves among the rocks on the seafloor,preferably at night. It surprises its prey and makes skillfuluse of its tentacles and jaws, which can rotate.

Speedy EscapeThe flow of water into and out of the funnel isregulated by alternately contracting and

relaxing ring-shaped muscles and long muscles. Byregulating the force at which the water is expelled, theoctopus can flee at high speed through a kind of jetpropulsion. The octopus moves in the direction its headis pointing, with its tentacles outstretched.

EYESAre located on thehead. The octopus'ssense of sight isexceptionally welldeveloped.

SELF-DEFENSE WITH INKA gland located near the anuscontracts when the octopussenses danger, expelling afluid that creates a dark cloudin the water.

SKINThe skin is a highlyelastic membrane thatcompletely covers theoctopus.

TENTACLESAll eight tentacles have the samelength. In the male, one tentaclefunctions as a genital organ.

The funnel muscles can actas a mechanism for fleeing.Rather than directing thefunnel forward, though, theoctopus directs it toadvance toward its prey.

The tentacles stretchforward and outward asthe octopus advances.

Using the wide area at the base of itstentacles, it envelops the prey.

MOUTHThe mouth of anoctopus has hard,chitin-like jaws forbreaking shells.

HEADThe head compresses andexpands, depending on theoctopus's breathing andmovements. The head containsthe brain but without a rigidprotective structure.

The FunnelThe funnel is the exit fromthe octopus's respiratorycavity. It is also extremelyimportant for the creature'smovement. The gills, insidethe mantle, absorb oxygenfrom the water. When thecavity fills, the gillsexchange oxygen for carbondioxide to be emptied fromthe cavity.

Masters of ColorFor the octopus, taking on the color of theocean floor is a camouflage strategy to hidefrom its prey. In deeper waters, anothertactic is to become luminescent toattract the prey. But when theoctopus changes colors while doinga certain dance, it is tryingto attract theopposite sex.

Large PredatorsDepending on its size, an octopus (likeother large cephalopods such as thenautilus, cuttlefish, and squid) iscarnivorous and eats both fish and otherinvertebrates: mollusks and crustaceans,especially crabs. It secretes a venomwith its saliva to finish killing the preybefore swallowing it.

Maximum speed of a fleeing octopus.Its speed is comparable to that

of a fast-walkinghuman.

4 milesper hour

(6 km/h)

Grasping AbilityAn octopus often crawls among the rocks. Using thesystem of suckers, or adhesive discs, on its tentacles, anoctopus clings to the seafloor or supports itself byattaching the suckers to the surfaces it encounters. Bygrasping with its forward tentacles, it can drag the restof its body in that direction.

INVERTEBRATES 33

MUSCLESPowerful and versatile, withself-controlled movements,an octopus can move theentire weight of its body.

SUCKERSArranged in two rows onthe lower surfaces forclinging to rocks and forgrasping prey.

A SPECIAL FAMILY 44-45

QUALITY SILK 46-47

SIXTH SENSE 48-48

POISONOUS STING 50-51

Crustaceans and Arachnids

Spiders, snakes, ticks, and mitesall belong to the same class,Arachnida. They are coveredwith sensory hairs so tiny thatthey cannot be seen by the

naked eye. In Greek mythology, Arachnewas a woman who challenged the goddessAthena to weave faster than she herselfcould. This angered the goddess, whoturned Arachne into a spider, forcing her

to weave forever. That is where thesecreatures get their name. Within the worldof crustaceans, well-known animals suchas the shrimp, lobster, and crab are alsodiscussed in this chapter. You will find

details about their anatomy, theirdifferences and similarities, and the wayin which they live that will surprise you.Some species breathe through gills andalso breathe through their skin.

COLORFUL ARMOR 36-37

CHANGING OUTFITS 38-39

SHARP FRONT LEGS 40-41

IN THE MIDDLE OF THE CHAIN 42-43

COLORFUL ARACHNIDSome species of the family Trombidiidaecatch our attention because of theirintense red color and the velvet-like

appearance of their hair.

Colorful Armor

36 CRUSTACEANS AND ARACHNIDS

Even though they inhabit all known environments, crustaceans are mostclosely identified with the aquatic environment. That environment is wherethey were transformed into arthropods with the most evolutionary success.

Their bodies are divided into three parts: the cephalothorax, with antennae andstrong mandibles; the abdomen, or pleon; and the back (telson). Some crustaceansare very small: sea lice, for instance, are no larger than one hundredth of an inch (aquarter of a millimeter). The Japanese spider crab, on the other hand, is more than 9 feet (3 m) long with outstretched legs, as it has legs in both the abdomenand the thorax in addition to two pairs of antennae.

INVERTEBRATES 37

APPENDAGESconsist of a lower regionfrom which two segmentedbranches grow, one internal(endopod) and the otherexternal (exopod).

Malacostracais the name given to the class of crustaceans thatgroups crabs together with sea lobsters, shrimp, woodlice, and sea lice. The term comes from Greek, and itmeans “soft-shelled.” Sea and river crabs have 10 legs,and one pair of these legs is modified in a pincer form.Malacostraca are omnivorous and have adapted to agreat variety of environments; the number ofsegments of their exoskeleton can vary from aminimum of 16 to more than 60.

MOVABLEFINGER

CEPHALOTHORAX

EYE

BRANCHIALCLEANER

BACKBRANCHIA

FRONTBRANCHIA

BRANCHIALCHAMBER

BRANCHIALCHAMBER

MULTIPLE FUNCTIONSAll crustaceans have anumber of appendagesthat are modified fordifferent and variedfunctions, depending onthe species..

FRONT LATERALMANDIBLE

FIXEDFINGER

ABDOMEN(PLEON)

BARNACLESWITHOUT A SHELL

SEA LICE

BARNACLECOLONY

THREE-LAYERED SKELETONIts interior part can containup to 80 percent chitin.

EXOSKELETONThe greater its number of segments, the lesshighly evolved the species.

MOUTH

PINCERSare the front pair oflegs. They are used tocatch food.

SHELLThe shell is hard andmeasures about 2.5inches (6.0 cm) across.

SEGMENTSThe back segmentsare smaller, andwhen they bend,they help enclosethe animalcompletely.

LEGSThis specieshas seven pairs of legs.

Together ForeverAt birth, barnacles (Pollicipes cornucopia)are microscopic larvae that travel throughthe sea until they reach a rocky coast.Then they attach themselves to the shoreby means of a stalk, which they developby the modification of their antennae, andthen form a shell. Once they are attached,they remain in one spot for the rest oftheir lives, absorbing food from the water.Barnacles are edible.

Wood Louse(Armadillidium vulgare)This invertebrate, belonging to the orderIsopoda, is one of the few terrestrialcrustaceans, and it is probably the one bestadapted to life outside the water. When itfeels threatened, it rolls itself up, leaving onlyits exoskeleton exposed. Even though it canreproduce and develop away from the water, itbreathes through gills. The gills are found in itsabdominal appendages and for this reason mustbe kept at specific humidity levels. That is alsowhy the wood louse seeks dark and humidenvironments, such as under rocks, on dead orfallen leaves, and in fallen tree trunks.

Copepodaare tiny crustaceans that form part of plankton. Copepoda play a veryimportant ecological role because they are a source of food for many marineanimals. There are more than 10,000 species of copepoda. Most are marinespecies, though there are also some freshwater species. The majoritymeasure between 0.02 and 0.1 inch (0.5-2 mm) long; the smallest ones

(Sphaeronellopsis monothrix) reach only 0.004 inch (0.11 mm) in length,and the largest (Pennella balaenopterae) are 13 inches (32 cm) long.

Young crabdevelops pincers

and migrates to lesssaline waters.

5

THE CRAB'S LIFE CYCLEEven though it is well adapted to variations in the salinity of the water, thefemale crab, after mating, always moves to saltier waters and lays her eggsthere. The larvae will go through different stages before becoming crabs.

The prawn is a 10-leggedcrustacean that lives in deep

waters and is able towithstand great

variations in thesalinity of its living

environment.

EUROPEAN GREEN CRABCarcinus maenas

is a littoral crab that lives on mostcontinents and that has become aplague. It comes in a variety of colors.

THE PACIFIC SPIDER CRAB CAN WEIGH UP TO

45 pounds(20 kg).

Mouth

Shell

Shell

Soft area

Head

Antennae

Segmentedlegs

Anus

Legsextended tocatch food

Rolled-upanimal

Extendedanimal

EXOSKELETON Divided intoindependent parts

SHRIMP AND CRABSMacrobrachium sp.

MegalopsIn the sea or river bed,

the larva grows seven to eighttimes its original size..

4

BARNACLE TRANSVERSAL CUT

THE FEWER THE SEGMENTS FORMEDBY ITS BODY, THE MORE HIGHLY

EVOLVED THE CRUSTACEAN.

Evolution

Egg needs a saline

environment forits development.

2

SpawningThe female lays her eggs in deep-water beds.1

ZoeaAt first,

the crab is aswimming larva.

3

Changing OutfitsT

he lobster belongs to the crustaceans, which are characterized by, among otherthings, an exoskeleton that supports and protects the body of the animal. Theexoskeleton has both advantages and disadvantages. The stiffness of the

structure prevents growth, which is why the animal grows only when the shell isrenewed. This process is called molting. During molting the layers of the newcuticle harden, and minerals and materials from the old exoskeleton arereabsorbed to create a new exoskeleton.

Chitinous ExoskeletonThe hard pincers help the lobster get food, and thesegmented body allows for movement. However, the

exoskeleton is a disadvantage in small places, because itcannot change shape. Even though theexoskeleton protects the lobster fromabrasive contact, it can harm itonce it breaks, because the fissurewill not mend until the next molting.

38 CRUSTACEANS AND ARACHNIDS INVERTEBRATES 39

AND NOT STOPGROWING

IN ALL THAT TIME.

A LOBSTER CAN LIVE

100years

THE LOBSTER MOLTS

once ayear.

EXOSKELETONis made of a substance calledchitin, which is strengthened by calcium salts. In theexoskeleton molting process, the new layers are formed in the cuticle; they then detach from the epidermis and form a new shell. This process uses a large amount of metabolic energy.

DOLPHIN-LIKE TAILThe tail is used forswimming. The bending ofthe tail and the abdomenpropel the lobsterbackward and forward.

NEW TAILSEGMENT

TELSONSEGMENT

In a Stranger's HomeHermit crabs belong to the Paguridae and Coenobitidae families.Unlike other crustaceans, a hermit crab does not have a hardexoskeleton on its abdomen to protect it. This is why it usesshells from sea snails as protection for part of its body.

VULNERABLEWhile it waits for thenew exoskeleton togrow, the lobster hidesso it does not end up avictim of its predators.

COLORIts color varies from grayto green and yellow,including even shadings ofred and black.

WALKING LEGSFive pairs of legs, of whichone or more pairs aremodified into pincers.

MOVABLEEYE

ANTENNULE

PINCER-SHAPED LEG

ANTENNAE

NEW ARTICULATEDSEGMENT

SEGMENTED ABDOMENThe lobster is made ofsegments with appendagesthat give its body itshardness.

CEPHALOTHORAXis formed by the abdomenand the fused segments ofthe head and the thorax,all of which are covered by the shell.

Shell

EpicuticleCuticleEndocuticle

Epidermis

Lower membrane

Between 30and 40 days

before ecdysis, newbristles form, andthe epidermisdetaches itself.

2

Hours before thebreak, the lobster

takes in large quantitiesof water until it fills upand breaks the oldexoskeleton.

3

FROM THE BURSTING OFTHE FIRST SKELETON

Once the crabreaches

adulthood, itsexoskeleton coversits body without anychange for about300 days.

1

During ecdysis itself, thelobster remains immobile

for approximately 12 hours,while it grows in size becauseof hydration.

4

HERMITCRABDardanusarrosor

LOBSTERPalinuridae argus

Molting of the ExoskeletonThe presence of the stiff exoskeleton means thatcrustacean growth takes place during the molting cycle.

This phenomenon occurs cyclically and frequently in the young ofthe species, with longer periods between molts as the crabmatures. During ecdysis (when the crab molts), the old shellbreaks and detaches, and the animal is helpless. Many functions,such as reproduction, behavior, and metabolic processes aredirectly affected by the physiology of the molt.

Crustaceans have appendages that generally branch in two directions and are adapted toaquatic life. A characteristic shared by all crustaceans is their articulated shell, whichleaves two pairs of antennae uncovered. They also have a pair of mandibles, two pairs

of maxillae, and a pair of appendages in each segment of the body. Their pincers have enoughstrength so they can trap their prey and feed themselves. The class Malacostraca includeslobsters, crabs, shrimp, and prawns, among other animals.

Sharp Front Legs

40 CRUSTACEANS AND ARACHNIDS

ANTENNAEThe brain receives the informationsent by the antennae andcommunicates with the rest of thebody through the ventral nerve.

AT RESTThe body remains close to the ground,the center of gravity is lowered, andmovements are slow and rhythmic.

PENDULUMSLOW WALKThe body operates like the weight of a pendulum. Close to the ground,it saves energy by moving in aswinging motion.

REBOUND EFFECTFAST WALKSuspended from its joints, thebody jumps by means of themand on them and multiplies theenergy of its movement.

PINCERSare mobile appendages thatit uses for defense andattack. With its pincers, theshrimp can trap its prey witha great deal of pressure sothat it cannot escape.

TENDON

CRUSHING CLAWTEETHThe lobster has thick, strongteeth and a muscle capable ofcrushing snail shells, clams, andeven a human finger.

CUTTING CLAWCUTTING EDGEThinner and with sharpedges, it is used to cutthe meat of its prey.

FLEXOR MUSCLE

WALKINGLEGSare situated in thecephalothorax, and eventhough they are rather smallin relation to the body, theyare capable of providingmovement.

NERVES

ARTERY NETWORK

SMALLCLAWSTwo small, movable pairsof claws bring food tothe lobster's mouth.

UROPODSare shaped like a spade.The telson is like a barb.Both are used by theshrimp for itscharacteristic escapebackwards.

JOINTS AND LEVERSCrustaceans, with slim limbs and little space forlarge muscles, are able to move with greatstrength because the majority of their jointsfunction as simple levers, with the lever armcorresponding to the limb itself, and the fulcrumcorresponding to the joint.

TELSONFin-like structures used forswimming. The telsonmakes up the caudal fantogether with the lastabdominal segment andthe uropods. There are noappendages.

Shrimpis the name for about 2,000 species of crustaceans of the suborderNatantia. Shrimp are characterized by their semitransparent and flatbodies, with appendages modified for swimming, and by their longantennae. Their length varies between 0.1 inch and about 8 inches (froma few mm to 20 cm), depending on the species. They live in salt water,brackish water, and fresh water. They survive by burying themselves for almost the entire day and coming out at dusk to catch their food.

CrabOf all crustaceans, the crab has surprising mobility andagility. It has five pairs of legs, four of which are walkinglegs, despite the fact that it moves laterally instead offorward. The crab-like movement is due to the placementof its legs and the general design of its body. A crab'swalk is funny, but its technique is effective for bothswimming and walking, even over such varied surfaces asbeach sand, rock, and Ωfor some speciesΩ tree branches.

LobsterA lobster is characterized by two enormous pincersformed by the first pair of legs. It lives on rockybottoms in shallow water, and it migrates seasonallytoward the coast in summer and to greater depthsin winter. The lobster is typically a nocturnal animalseeking its food when the Sun sets. Its food consistsmainly of mollusks, bivalves, worms, and fish.

2

1

3

LIVING SPECIES AND AS MANYFOSSIL SPECIES ARE PART OF THIS

GROUP OF INVERTEBRATES.

55,000

PLEOPODSFirst five pairs ofabdominal appendages

FIRST TWO PAIRShave been adapted forsexual functions.

LAST THREE PAIRSare similar to each otherand are used to swim.

DUBLIN BAYPRAWNNephropsnorvegicus

LOBSTERHomarus vulgaris

PEREIOPODSFive pairs of appendages

FIRST THREE PAIRSare used to feed itself. The pincers catch and hold prey.

LAST TWO PAIRSwork as walking legs thatare aided by the pleopods.

MuscleMuscle

Joint

Resistancepower

FRONTVIEW

The body, elevated higherthan its joints, tends to falllike an inverted pendulum,which helps with movement.

INVERTEBRATES 4342 CRUSTACEANS AND ARACHNIDS

In the Middle of the ChainZ

ooplankton include thousands of distinct species belonging to very different groups. Amongthese species are protists, coelenterates, worms, crustaceans, and other small, weakly swimmingorganisms. Unicellular, eukaryotic protists constitute a large group of species of zooplankton. They

constitute an extensive and varied community in the food network. The phytoplankton, which are capable ofphotosynthesis, provide food for the zooplankton. Phytoplankton also serve as food for echinoderms,crustaceans, and larval-stage fish. Once they grow up, the larvae serve as food for schools of small fish, whichare in turn food for larger fish, including plankton-feeding whales that sometimes eat these small fish.

The krill makes use of its telson,comprising five paddles, to drive itselfthrough the water. It reaches greatspeed and moves jumping forward and

backward. These crustaceans group ingiant schools, with thousands ofindividuals concentrated in each cubicyard of water.

HOW IT FLEESThe food cycle is initiated with a vegetable producer,which begins the chain for consumers. Those that feed onproducers are primary consumers, those that feed onprimary consumers are secondary consumers, and so on.

TROPHIC CHAIN

Is one of the most abundant andsuccessful species on the Earth.Krill can live five to 10 years,experiencing 10 moltings beforereaching their maximum length.Krill typically emit a greenishlight that can be seen at night.

KRILL Euphausia superba

MalacostracaAre typically oceanic, though some haveadapted to fresh water, and others are evenadapted to life on land. All have a bodydivided into a 13-segment cephalothoraxwith 13 pairs of appendages, a stomachwith six segments, and, at the extremeposterior, an unsegmented telson.

Brachiopodshave a body of variable segmentation, usually abivalve shell, supplied with leaflike appendages forlocomotive and brachial functions (hence thename brachiopod). They are abundant in lakes andstill water, feeding on debris and microscopicplants. Because there are few males, eggs from afemale can develop without fertilization in newindividuals, a process known as parthenogenesis.

Copepodsare aquatic microcrustaceans, thoughterrestrial ones also exist. They are foundin fresh water as well as in salt water.They feed on phytoplankton and are animportant component of plankton, whichat the same time serves as food fornumerous marine animals.

6,600 feet (2,000 m)

DEPTH TO WHICH SWARMS OF KRILL MAY GATHER

12,000SPECIES OF COPEPODS

6 to 8 weeksIS THE AVERAGE LIFESPAN OF A WATER FLEA.

REAL SIZE1.5 inches (3.8 cm)

has two pairs of antennae and feet adaptedto swimming and grasping. The secondantenna pair serves as a locomotive organ.The water flea feeds on microscopic seaweedand the remains of dead animals.

WATER FLEA Daphnia sp.

REAL SIZE

0.1 inch (3 mm)

Cyclopoid copepod larvae are luminescent.After their developmental stage they begin to swim freely. The cyclopoidcopepod lives in fresh water. It is amongthe most numerous invertebrate species found in Europe.

CYCLOPOID COPEPODMegacyclops viridis

REAL SIZE

0.08 inch(2 mm)

Octopuses, penguins, fishSecondaryconsumers

Right WhaleTertiaryconsumers

ZooplanktonPrimaryconsumers

PhytoplanktonProducers

NAUPLIUS LARVA Cyclops sp.

This little crustaceanswims by jumping withits legs. It feeds onanimal and plant remains.

LARGE APPENDAGESThey form very fine combsthat filter the water for food.

LEGSWith their featherylegs krill filter out thesmall algae on whichthey feed.

LUMINESCENCEEach specimen of krill has a photophore in itsabdomen, a structure that allows it to emit lightbecause of a chemical reaction that involvesoxygen and various other chemical compounds

called luciferin, luciferase, and adenosinetriphosphate (ATP). One order of crustaceans

is generically known as krill.

EYEKrill have only onelarge, compound,black eye.

FEETattract the watercurrent toward thelarva's mouth, whichlittle particles can enter.

0 second 0.5 second 1 second

10 inches(25 cm)

20 inches (50 cm)

10,000

1,000

100

10

A Special Family

44 CRUSTACEANS AND ARACHNIDS

Arachnids make up the largest and most important class ofchelicerata. Among them are spiders, scorpions, fleas, ticks,and mites. Arachnids were the first arthropods to colonize

terrestrial environments. The fossil remains of scorpions are foundbeginning in the Silurian Period, and they show that these

animals have not undergone major changes in theirmorphology and behavior. The most well-knownarachnids are the scorpions and spiders.

INVERTEBRATES 45

Tick

Tick

Visible dorsalcapitulum withdorsal projectionsthat can beremoved easilyfrom the tick.

Palps

Salivaglands

Middle stomach

Adhesionmaterial

Infection

Palps

Growth happens through molting, a process bywhich the spider gets rid of its old exoskeleton.In its youth the spider grows through successivemoltings (up to four a year), and once it reachesadulthood, it goes through a yearly change.

EXOSKELETON

AmblypygiSmall arachnids measure between 0.2and 2 inches (0.4 and 4.5 cm). Thechelicerae are not as large, though thepedipalps are strong and are used tocapture prey. The first pair of legs aremodified touch-and-sensingappendages, whereas the last threetake care of movement. Because of aspider's flattened body, its walk issimilar to that of the crab.

Mite

IS THE NUMBER OFSPECIES OF ARACHNIDSTHOUGHT TO EXIST IN

THE WORLD.

100,000

PEDIPALP ARACHNID Phryna grossetaitai

Spidersare the most common arthropods. They havethe surprising property of secreting asubstance that, on contact with the air,creates very fine threads that spiders skillfullymanage for diverse purposes. Once a femalespider mates, she deposits her eggs inside acocoon of special silk, called an egg sack. Theappearance of spiders is unmistakable: the twomain sections of the body, the thorax (alsocalled a prosoma) and the abdomen (alsocalled an opisthosoma), are united by a narrowstalk (the pedicel). Spiders have four pairs ofeyes, whose distinctive size and placementhelp characterize different families of spiders.Their chelicerae end in fangs that carryconduits from venom glands. Spiders kill theirprey by using their chelicerae to apply venom.

The female cantransport up to 30offspring on its back.

The claws holdthe prey andimmobilize it.

Palps

The front edge of theshell comes off, and

the tegument separatesfrom the abdomen.

1The spider raisesand lowers its

legs until the skin slipsand falls.

2

It removes the oldexoskeleton, and

the new one hardens oncontact with the air.

3

WALKING LEGSThe spider has four pairs of legsfor walking. The hairs help it torecognize terrain.

This spider is distinguishedby its long legs in relation

to its body.

GIANTHOUSEHOLD

SPIDERTegenariaduellica

STOMACHVENOMGLAND

OVARIES

LUNG

HEART

INTESTINE

GENITALORIFICE

SILK GLAND

PEDIPALPS

SIMPLEEYE

CHELICERAE

CLOACA

CEPHALOTHORAX(PROSOMA)

ABDOMEN(OPISTHOSOMA)

PEDIPALPS The terminal pedipalp forms acopulating organ through whichthe male inseminates the female.

PATELLA

TIBIA

METATARSUS

TARSUS

IN LENGTH.

WITH ITS LEGS SPREAD OUT, A SPIDER CAN MEASURE

12 inches(30 cm)

FEMUR

ScorpionsFeared by people for ages, thescorpion is characterized by thefact that its chelicerae (mouthparts that in scorpions are large)and pedipalps form a pincer. Thebody is covered with a chitinousexoskeleton that includes thecephalothorax and abdomen.

act as sensory organs and manipulate food.Males also use them for copulation.

CHELICERAEmove up and down.In the more primitivespiders (such astarantulas), thechelicerae move sideto side like a pincer.

Mites and TicksBoth are members of the Acari order. They are differentiated by their size. Mites aresmaller; ticks may measure up to an inch in length (several centimeters). Mites have manydiverse forms and are parasites of animals and plants. Ticks have a common life cycle ofthree stages: larva, nymph, and adult, during which they live off the blood of their hosts.

Like other scorpions, it has astinger crisscrossed byvenomous glands. Itmeasures between 5 and 7inches (12 and 18 cm) long,though some have reached alength of 8 inches (20 cm).

EMPEROR SCORPIONPandinus imperator

INVERTEBRATES 4746 CRUSTACEANS AND ARACHNIDS

Quality SilkS

piders are known for the production of silk,with which they construct spiderwebs. Withthe threads made in their glands, spiders can

capture prey, defend themselves, or care for theiroffspring. Seven types of silk-secreting glandsare known, but no spider has all seven typesat one time. Inside the gland, the silk thatspiders produce is liquid, though itemerges as a solid fiber.

SPINNERETSThe silk emerges throughspinnerets; the thin threads arejoined to each other before theydry to form a thicker strand.

SILK GLANDMoves the silk to the spinnerets.The secretion is a liquid substancethat is insoluble in water.COMPOSITION

The silk is made of complexproteins. Males as well as femalesgenerally have five to sevendifferent types of special silk glandsfor producing these proteins.

Threads of SilkThe silk thread made by spiders is produced in twoor three pairs of spinnerets that contain hundreds

of microscopic tubes that lead to the abdominal silk-producing glands. The thread emerges as a liquid thathardens upon being secreted by the spinnerets.These masters of weaving produce many threadsat once. When secreting the silk substance, ascleroprotein, spiders cover it with a thin, fattylayer. Scientists believe that some spiderwebsimitate the ultraviolet images of flowers. Suchimitation lures many butterflies and bees tofall into the spider's sticky trap.

BEGINNINGThe threads set up a bridge.The spider lets itself sway inthe wind until it falls andfinds its footing.

1

TRIANGLESThe spider adds a loose threadfastened to each side of thebridge, moves to the middle ofthe bridge, and lowers itself toform a triangle with the silk..

2

SUPPORTThe spider creates the supportstructure that it will attach toa nearby object. This objectmight be a tree trunk, a wall,or a rock.

3

RADIUSWith the silk glands (glandulaeampullaceae), the spiderconstructs the spokes of theweb. Dry strands that runfrom one spoke to the nextform a spiral.

4

REPLACEMENTDry web material breaks fromthe action of the chelicerae andfrom food trapped in the web.The spider replaces this brokenmaterial with stickier andthicker silk.

5

ArchitectureThe appearance of a spiderweb depends on thespider that wove it. There are very well-designed

structures, such as the hammock web built under bushesby the tiny Linyphia triangularis. Other webs, such asthose of the families Linyphiidae and Agelenidae, are notmade of sticky silk but only a dry variety. The silk ofthe spider is almost as strong as steel, and ithas double the elasticity of nylon. Somegiant tropical spiders build spiderwebsthat are as strong as fishing nets,with which they can trapeven birds.

Diverse Uses of ThreadIn addition to spiderwebs and traps, and shelter lining, spider silkhas other uses. The spider can use it as a thread for tracking its

position or as a safety thread when it either lowers itself or is suddenlydislodged and falling. A spider can also use the silk thread to suspenditself in midair. Male spiders use silk as a web where they deposit theirsperm before leaving in search of a female, who uses the silk to build eggsacks, where she will deposit her eggs.

The amount that athread of silk can stretchfrom its original length30%

THE NUMBER OF RECORDED SPECIES OFWEB-SPINNING SPIDERS

2,500

WEB

LINING SPERM

EGG SACK

FABRICATION

SECURITY

EYELETAllows for 360-degree vision.

EYEThe retina inside the eyecan move in threedimensions, whichpermits the spider tolook in all directions andfocus on an object.

PEDIPALP Appendage usedto get to knowthe environment

CHELICERAEAppendage with a fang thatsecretes venom

TRICHOBOTHRIAis a long, tactile hair.

TACTILE HAIRperceives thesensory flow of theenvironment.

ReactionThe hair does not bend,and the angle decreases.

Trichobothriaperceivesmovements.

ReactionThe hair curves, andthe angle is greater.

ActionContact withan object

ActionContactwith the air

Chelicerae and EyesChelicerae are formed by two segments: a basalsegment that contains the venom gland and the

rest of the appendage that forms a fang at the end ofwhich the venom channel opens. Normally spidershave eight simple eyes, each one supplied with a singlelens, optical rods, and a retina. The eyes are basicallyused for the perception of moving objects, but somecan form images.

Pedipalps: Various Functions The pedipalps consist of six segments and havepincers; they are tactile along almost all of their

length, and in the males the ends are modified to form areceptacle that transfers the sperm during copulation. Thelower parts of the pedipalps are used for chewing.

Sixth SenseS

piders do not have good vision and can seeonly a short distance. For this reason, theycarry out many of their activities at night.

However, some spiders do have sharp vision. To beaware of the world around them, spiders use thesensory hairs that are located at the ends of theirlimbs. Each body hair is sensitive to differences in pressure. Some hairs are also capable oftransmitting vibrations to the exoskeleton.

48 CRUSTACEANS AND ARACHNIDS INVERTEBRATES 49

OGREFACEDSPIDER Dinopis sp.Two powerful eyes

JUMPING SPIDERPhidippus audaxFour large eyes on thefront of its head and foursmaller eyes on the upperpart of the head.

DYSDERA CROCOTADysderaSix small eyes

CRAB SPIDERXysticus cristatusEight spread-out eyes

THORN

TIBIA

TARSUS

TUFT OF HAIROF A CLAW

HAIR (TARSALORGAN)Senses humidity

HairsAre used to conduct stimuli to the cells. Some areshort and stiff, others long and flexible. According

to the form of the hair, the mechanoreceptors providethe spider with information about the world thatsurrounds it. The stimuli induce the animal to flee fromenemies, obtain food, and establish the reflexes neededto walk, run, fight, or mate.

Exocuticle

Sensillae

Hairs that feelvibrations and sensethe presence ofstrangers

Hair-likesensillae

Integumentarygland

Endocuticle

Epidermis

Sensorycell

INVERTEBRATES 5150 CRUSTACEANS AND ARACHNIDS

Poisonous StingV

enomous arachnids are the group of arthropods most feared by people. Even if a bitemay be fatal to another animal, it is unlikely that it will be fatal to a human being, whowould be attacked only as a means of defense in cases of fear or danger. The scorpion

stands out among the most dangerous species. It uses its stinger when it wants to be certainof catching a difficult prey. Another notable example is the black widow, whose tiny bodyproduces one third as much venom as a rattlesnake.

TELSONSTINGERIs located inthe lastsegment.

DETECTS THE PREYThe scorpion does not go outin search of food; rather, itwaits until food passes by it.The scorpion can also findfood by accident.

CLOSES INThe scorpion directs the front ofits body toward the animal,approaching to a distance of 2to 4 inches (5 to 10 cm), when itlowers its pedipalps inpreparation for attack.

ATTACKOnce the scorpion is close to itsprey, it walks around the victim,trapping it. Then it uses itspedipalps to contain theattacked animal.

USE OF THE STINGERIf the prey resists, the scorpion uses itsstinger to inject the venom. Venom isadministered by the scorpion until it kills the animal.

OPISTHOSOMAABDOMEN

VENOM GLANDSThe secretion comesout through conduitsthat open near the tipof the stinger.

PECTENThis structure is made upof numerous sensorystructures,mechanoreceptors, andchemoreceptors.

PROSOMACEPHALOTHORAX

SCORPIONSScorpions are grouped in six families, themost important being the Buthidae because

it contains the most dangerous species for thepotency of their venom. The flat form of theirbodies helps them hide under rocks, tree bark,and various kinds of debris. Scorpions havenocturnal habits. Cannibalism is common amongscorpions, especially after copulation. The onlyplaces in the world where there are no scorpionsare Antarctica and Greenland.

The Most DangerousOf the 38,000 known species of spiders, only about30 have venom that is harmful to humans. Some

are hunters or trappers, but others are small, peacefulweavers. The black widow (Latrodectus mactans) is oneof the shyest. The venom that it injects (toxalbumin) is aneurotoxin that acts principally on the nerve endings.Still, the black widow bites only when provoked. Thewandering spider (Phoneutria fera) is one of the mostaggressive arachnids. It is large, and its venom is fast-acting, capable of killing most prey in 15 minutes.

Conduct ofCapture and StingScorpions have long, fine hairs calledtrichobothria, located in the pedipalps. Theseperceive the vibration and movement of thewind and help the scorpion detect flying preyand predators. These organs help the scorpionget out of harm's way when danger threatens.

PEDIPALP

CLAW

DESERT SCORPIONHadrurus arizonensis

COMPOSITIONOF VENOM

CHELICERAEBecause the hunting spider does not have a jaw, it has to useits chelicerae to take its food apartwhen it feeds. The chelicerae arealso used during copulation.

HUNTING SPIDERHeteropoda venatoria

Spider venom is a cocktail of substances,particularly potassium salts, digestive enzymes,and polypeptides. The potassium alters theelectrical balance in the nerves and paralyzesthe victim. The peptides disable the cardiacmuscles and can also attack the nervoussystem or cause pulmonary edema.

HOW THE STINGER WORKSTwo conduits run from the venomglands to openings at the end of thetelson. When the scorpion stings,muscles press the walls of thetelson against the venom glands toforce venom through the hole of thestinger into a wound. This process iscontrolled by the scorpion, whichadministers the proper dose ofvenom, since it cannot quicklyregenerate the venom if it fails.

CENTRAL EYE

METASOMATAIL

of spiders have trulydangerous venom.

30species

2

1

3 4

MUSCLES

PALP OR PEDIPALP

METAMORPHOSIS 70-73

ORDER AND PROGRESS 74-75

GOAL: SURVIVAL 76-77

ONE FOR YOU,

ONE FOR ME . . . 78-79

Insects make up the largest andmost varied group of arthropods.Most reproduce easily, and thereare insects adapted to anyenvironment. Their bodies are

protected by a form of armor.Arthropods are currently believed to bethe only living things capable ofsurviving a nuclear winter. They havehighly developed sensory organs that

enable them to see long distances. Thediversity and sheer number of insectspecies, estimated at 1.5 million, are atestimony to their evolutionary success.They have been successful, in part,

because they are small, need less foodthan larger organisms, and haveextraordinarily developed means ofmovement that keep them from beingeasy victims for predators.

GREAT WALKERS 62-63

HIGH-QUALITY JUMPERS 64-65

THE ART OF FLYING 66-67

DIVING, SWIMMING,

AND SKATING 68-69

THE SECRET OF SUCCESS 54-55

THE BETTER TO SEE

YOU WITH 56-57

TYPES OF MOUTHS 58-59

SUCKING AND PIERCING 60-61

Insects A PECULIAR SENSE OF SIGHTThis tropical insect has a pair of eyes on each side of its body,giving it a very wide field of vision.

INVERTEBRATES 55

STRUCTUREgives the wingsgreat stability.

SPIRACLESSmall entrances tothe tracheae

APPENDAGEcontains thegenital organs.

HUNTINGThe front legsenclose the prey.

ANTENNAE

EYES

LEGS

HIND WINGS

AT RESTDragonfliescan placetheir wingsagainst theirbodies.

Two Pairs of WingsSome ancient species had three pairs ofwings. Today, however, insects have one ortwo pairs. Butterflies, dragonflies, bees, andwasps use two pairs to fly, but otherinsects fly with only one pair.

OPEN CIRCULATIONA tubular heart pumps the hemolymph(blood) forward through the dorsal aorta.Accessory contracting organs help pushthe blood into the wings and legs.

RESPIRATORYSYSTEMLand-dwelling arthropodsbreathe with tracheae.Through branching tubes(tracheoles), air containingoxygen is brought directlyto each cell, and carbondioxide is eliminated.

Sensory antennae, appendages on the head that can be used to chew, crush, or grab, highlydeveloped eyes on the sides of the head, and pairs of jointed legs with functions thatdepend on the speciesΩall are outstanding common features of insects and millipedes

(subphylum Myriapoda). Insects, also called hexapods, have six legs attached to the thorax.Myriapods are multi-segmented arthropods that have developed only on land.

BILATERALSYMMETRYThe entire body of

insects and

myriapods is

composed of pairs,

arranged along an

imaginary axis

that passes from

the head to the

lower end of the

abdomen.

HEAD

THORAX

ABDOMENImaginaryaxis

DRAGONFLY

HAWKERDRAGONFLYAeshna cyanea

JAPANESERHINOCEROS BEETLEOdontolabis wollastoni

CENTIPEDEScolopendra sp.

MILLIPEDESphaerotheriidae sp.

1 millionKNOWN INSECT SPECIES

DIGGINGMole cricket

GATHERINGBee

FAN-SHAPEDCedar beetle

KNOBBEDButterfly

FILIFORMLocust

FEATHERYMoth

SWIMMINGWater scorpion

WALKINGCockroach

JUMPINGGrasshopper

Segmentsare calledmetameres.

LegsTwo pairs persegment

Taking Many StepsThe class Chilopoda (centipedes, includingmany carnivores and predators) and the classDiplopoda (millipedes) are known as myriapods.Their patterns of movement are both complexand efficient.

Sensing andCommunicating Antennae are sensory organs. Theyenable the insect to communicate, andthey contain cells shaped like threadsor plates. Antennae are adapted inmany ways that enable insects to feel,perceive sounds, sense the temperatureand humidity, and taste food.

JawsThe mouth apparatus of insects can be adapted forchewing, licking, sucking, or biting, depending on thespecies. Beetles (order Coleoptera) have pincer jaws withsensory organs.

SEGMENTED REGIONSInsects' bodies are divided intothree parts: the head (6 segments),the thorax (3 segments), and theabdomen (up to 11 segments).

Side-openingpincers

Sacs

Fingerjoint

LegsTARSAL SEGMENT

CLAW

FEMUR

TIBIA

LegsOne pair persegment incentipedes

Tracheoles

Tracheae

Bodywall

Muscle

THORAX

Antennae

The Secret of Success

54 INSECTS

Legs Adapted for Each Type of UseThe shape of the arthropod legs shown here is closely related totheir use and to the arthropod's habitat. Some species have tasteand touch receptors on their legs.

The Better to See You With

56 INSECTS INVERTEBRATES 57

Just as people without color vision have a hard time understanding what color is, it isimpossible for humans to imagine what it is like to see through the compound eye of aninsect. These eyes are made of thousands of tiny rods called ommatidia, each one a

small eye connected directly to the brain. Scientists theorize that the insect's braincomposes the images received from each ommatidium, enabling it to perceivemovement in any possible direction-in some species, even from behind.

A Bee's Eye ViewCompared with human vision, abee's vision is somewhatnearsighted. Even the imagesof nearby objects are blurry.Its compound eyes have some6,900 ommatidia.

LENSCone-shaped, todirect light tothe rhabdom

RETINALCELL

PIGMENT CELL

COMPOUND EYE

RHABDOMConnects eachlens with itsnerve

CORNEAHexagonal in shapeto fit into the rest ofthe compound eye

MOUTHThe mouth hasapparatus forlicking and sucking.

ANTENNA

4,000OMMATIDIA.

THE HOUSEFLY HAS

FLYDrosophila sp.

HEADED FOR NECTARSensitivity to ultravioletlight, invisible to the humaneye, enables worker bees to find the nectar inside the flowers.

HUMANSWith binocularvision, a flat andundistorted image

BEESIn a larger field, thesame image isnarrower.

Area withnectar

Field of Vision

Distortedmidline

ANTENNA

360ºFIELD OF VISION

OF A FLY

A fly's ommatidia are arranged in circles, and each one covers a portionof the field of vision. Such systems may not yield a high-resolutionimage, but they are highly sensitive to movement. The slightest motioncauses a transfer of sensitivity from one ommatidium to another. This is what makes it so hard to catch a fly.

Sections offield ofvision

Perceivedpath

Movingobject

35 inches

(90 cm) Human fieldof vision

Binocularfield

180° fieldof vision

OMMATIDIUM

CALCULATORSThis common bluedamselfly uses its eyesto calculate distances.

VISION IN THE ROUNDCertain dragonflies havea completely sphericalfield of vision.

PROTECTIVEThe eyelets of thetachinid fly coverits eyes.

TYPES OF EYES

One Eye, or ThousandsEach ommatidium is responsible for a small portion of the visualfield. Depending on the type of light they receive, the pigmentedcells around each rhabdom can vary their diameter, regulatingthe overall sensitivity of the compound eye.

FLYVISION

Retina

Eyelet

Ommatidia

Antenna

INVERTEBRATES 5958 INSECTS

Far from being a mere opening, the mouth isusually one of the most complex partsof an insect's body. The simple

oral appendages of the mostprimitive forms were graduallymodified so that this zoologicalgroup has been able to expand itsdiet. Thus, a hunter's mouth is totallydifferent from that of a sucking insect or aleaf-eater, such as the locust.

Types of Mouths

Made to orderThe oral appendages ofprimitive insects were

modified considerably, and theytook different forms according tothe species. The first pair of upperjaws is for holding and sucking thefood into the mouth. The secondpair of upper jaws fuses at themidline during its development toform the lip, a structure withdifferent functions, depending onthe diet. The lower jaws and thefirst pair of upper jaws are at theside of the mouth, and an upperlip, the labrum, protects the frontof the mouth. These parts formthe basic biting-chewingapparatus. In more advancedforms, its modifications give riseto structures for sucking andlicking or for biting and sucking.

THE TIME IT TAKES A LOCUST TOEAT ITS OWN WEIGHT IN FOOD

1 day

LOCUSTFamily AcrididaeSince ancient times, locustshave been feared as a greatplague on crops.

Strong lower jawsand dexterousupper jaws

Lip for nectar; lowerjaws to chew pollen andmold wax

With a small labrumand no lower jaw.The upper jaws forma suction tube.

The lip and upper jawsform a tube; the lowerjaws are for puncturingthe skin, and the labrumforms a sheath.

LOCUST

BEE

BUTTERFLY MOSQUITO (FEMALE)

Rightserratedlower jaw

Palps ofrightupper jaw

Lip withpalps

Labrum

Left upperjaw, withpalps

Leftserratedlower jaw

Eyelets

CARNIVORESuse their jaws aspincers to grasptheir prey.

Antenna

Compoundeye

Labrum

Lower jaw

Upperjaws

Lip

Lower jaw

Upper jaw

Lip

Antenna

Compoundeye

Antenna

Compoundeye

Upper jaws

Antenna

Compoundeye

Labrum

Lower jaw

Upper jaw

Lip

BITING ANDCHEWING

PIERCING ANDCHEWING

SUCKING PUNCTURING ANDSUCKING

SEVEN-SPOT LADYBUGCoccinella septempunctatafeeds on aphids, plant lice,and sand flies.

Leaf EatersInsects such as locusts and somebeetles, as well as caterpillars (and the

larvae of many other species) need a mouthstructure capable of cutting leaves into smallpieces and then putting them into the mouth.For this purpose their large lower jaws have aseries of serrated teeth, whereas the upperjaws and the lip have palps for manipulatingand grasping the leaf pieces.

LEFTLOWERJAW

PALP(ON LIP)

LABRUM

COMPOUNDEYE

ANTENNA

FRONT LEG

60 INSECTS

Starting with lower jaws adapted for chewing, manyinsects have developed a more sophisticated oralapparatus, which has enabled them to expand their

diet. Mosquitoes, for example, can pierce mammals' skin andfeed on their blood using one of the most complex mouths innature. Flies can eat solid food by using their oral apparatusto begin digestion outside their bodies. Other species havemouths that enable them only to drink liquids.

Suckingand Piercing

SUCKING

Heteroptera (true bug)

FlyMosquito

Butterfly

MOSQUITO (FEMALE)Aedes aegyptiThis species transmits yellowfever and dengue. Only thefemales bite, in order toobtain the proteins they needduring the time when theyare laying eggs.

COMPOUNDEYE

ANTENNAEThe mosquito'sthread-like sensoryorgans. To bite, itbrushes themagainst the skin ofits victim.

STYLETSFlexible tool used topierce and hold in place

PIERCING

The fly dampens andsoftens the food withsaliva and digestivejuices.

1 WETTING

These digestive juicesbreak the food downand turn it into apartially digested soup.

2 MAKING SOUP

Once the food isliquefied, the fly sips itup with its proboscis.

3 EATING

Shapes

The Fly

How the Mosquito Bites

With its stylets, the mosquitoperforates the skin to holditself in place and inserts thelabellum (lower end of theproboscis) through the skin.

1 PERFORATION After injecting salivato prevent clotting,the mosquito sips theblood of its victim.

2 ABSORPTION

AMOUNT OF BLOOD SUCKED BY AMOSQUITO IN ONE BITE

0.001-0.01 ml

LIPContains one tube forsucking and another fordischarging enzymes

feeds on soft, damp substances.It uses its mouth to put enzymesonto certain solids to soften themso it can sip them up.

UPPER JAWPALPS

Head

Eyes

Bloodrisesthroughthe tube.

Saliva

Blood

Antennae

DETAIL CROSS SECTION

Labrum

Upper

jaw

Lip

Epipharynx

Hypopharynx

Head ofthe fly

Eyes

Stylets

Lip

Tube for saliva

Tube forfood

DETAILCROSSSECTION

The ButterflyIts upper jaws are modified into aretractable tube. It feeds onaccessible fluids, such as nectar.

Upper jaw

Interlocking bristles

Tube fornectar

To eat, theinsect unfurlsthe tube.

When notin use, thetube isrolled up.

62 INSECTS

Great WalkersE

tymologically speaking, myriapod means “many feet.” The term refers to two very differentclasses of invertebrates: Class Chilopoda and Class Diplopoda, better known as centipedesand millipedes. All are animals divided into segments. Centipedes, most of which are

carnivores, have a pair of legs on each segment, and millipedes have two pairs of legs persegment. These invertebrates (which are not insects) have so many legs that, to walk, they mustuse a highly sophisticated timing mechanism that seems to follow mathematical principles.

ChilopodaThese centipedes use venom to paralyze potentialprey, generally small invertebrates. It is produced in

a gland near the head and is applied through themaxillipeds. When the adjoining nerve connections givethe order to contract the muscle of the maxillipeds, themechanism is put into motion, and the venom flowsthrough the internal duct. With few exceptions, it is not avenom harmful to people, although the bite is painful andproduces localized pain.

Applied MathTo walk, land-dwelling arthropods arch their bodies and move their sixlegs in coordination so that when one leg moves forward in a power

stroke, the ones in front, behind, and opposite it are in a recovery phase,remaining on the ground. Myriapods have a similar mechanism, although it ismuch more complex because of their large number of legs. The legs arejointed, but they do not function independently of each other for the arthropodto move forward. The segmented body moves side to side in a regular wavepattern, and the legs are functionally adapted to this body movement.

INVERTEBRATES 63

VENOM GLANDis located on the head of thecentipede. It is a sac that is putaway and stored until it is used.

JOINTED FEETThere may actually be many more than100: there are from 15 to 191 pairs.

MUSCLES AND NERVESform a system that allows the centipede tosqueeze the maxillipeds and apply thevenom through an internal duct.

MAXILLIPEDSThis is the name of the appendages locatedbetween the mouth and the first pair oflegs: they contain venom.

ANTENNAE It has only one pair. Theyare segmented and arerarely longer than the body.

SCOLOPENDRA CINGULATA(MEGARIAN BANDEDCENTIPEDE)

Typical size

Maximum size

Quantity of segments

4 inches (10 cm)

12 inches (30 cm)

20-40

Scolopendrida

Millipede, or diplopod, is the name of land-dwelling invertebrate species with multi-segmented bodies that have two pairs oflegs on each segment. They live in dampplaces and feed on decomposing material.All of them have a pair of simple eyes anda pair of antennae, lower jaws, and upperjaws. The largest do not exceed 4 inches(10 cm) in length.

A Thousand Legs

Not only does an arthropod'sbody move in wave patterns;when the legs on one side of itsbody are closest together, those onthe other side are farthest apart. Thisalternating pattern is repeated allalong its body.

SINUOUS PATH

Female centipedes lay eggs in thespring and summer. Theseinvertebrates can live up to sixyears, and it takes them threeyears to reach maturity.

A CENTIPEDE'S LIFE

There are species of centipedes thatadd segments throughout their lives;others are born with a fixed numberof segments that grow in size.

SIZE OR QUANTITY

They are long and flat and covered by a layerof chitin. They have one pair of legs for eachsection that forms the trunk. Centipedes liveon land and are almost all carnivores; manyare venomous. The head of the chilopod hasone pair of eyes in the back, consisting oftwo groups of eyelets, a pair of antennae, apair of lower jaws, and one or two pairs ofupper jaws. Almost all seek dark places,avoiding the light. These invertebrates canmeasure between 0.15 inch (4 mm) and 12

inches (30 cm) long.

Centipedes

LIKE CLAWSThe back legs of thiscentipede, almostperpendicular to the rest,are used to trap and holdprey while it injects itscatch with venom bymeans of powerful jaws.

1

DEADLY WEAPONHolding the prey with theback legs, the centipededoubles itself over, the tips ofthe maxillipeds (forceps)fasten like claws, and thevenom is discharged throughthe opening at the tip.

2

PredatorsAll centipedes are carnivorous andvenomous. The largest tropicalcentipedes can eat worms, insects,and even small birds and mammals.

SMALL BULLIESAn Australian centipede,like the one in thepicture, can make aperson sick for a weekwith its bite, and it iscapable of killing a dog.It measures 5 inches(12.5 cm).

1

CRUSHERSGeophilomorphahave a very longbody, are yellow incolor, and have 25pairs of legs; the lastdiverge from the axisof the body. Theirstrategy is to attachthemselves to aworm or earthwormuntil they crush it.

2

Order of JumpersFleas are in the class Insecta, orderSiphonoptera, which includes

wingless insects that are external parasitesand lack wings. Their mouth apparatus isfor piercing and sucking, and their life cycle

is one of complete metamorphosis. Their 16families include the genera of fleas thatinfest cats and dogs (Ctenocephalides canisand C. felis), as well as those that infesthens (Ceratophyllus gallinae).

Life CycleA complete cycle, from egg toadult, can take from two to eight

months. The length of the cycle varies byspecies and by temperature, humidity inthe environment, and the availability offood. In general, after feeding on blood,the female lays 20 eggs per day and upto 600 eggs throughout her life. Theeggs are laid on the host (dogs,cats, rabbits, mice, rats, opossums,humans, etc.).

Edible BloodAs parasites of warm-blooded animals,fleas are classified as hematophagous

(blood-eating) insects. Adults suck the blood oftheir hosts, which contains nutrients that they

use for their own nutrition. Females use thesenutrients to produce their eggs. The driedblood ejected in the adults' feces is also usefulas food for various types of larvae.

SuperproteinThe capacity to jump is related to thepresence of resilin, a protein of great

elasticity similar to rubber. Flea resilin has thefunction of building tension in the jumping legs.The release of accumulated energy generates

the jump. On occasion the jump is useless, andthe flea does not manage to place itself on thehost. Far from being a failure, the fall adds tothe tension of the resilin, which makes therebound a longer jump.

Quality JumpF

leas are well known for their extraordinary jumps. When theyare adults, these small, wingless insects take advantage of theirjumping ability to hunt for their food, the blood of birds and

mammals. They are ectoparasites of dogs, cats, and chickens, whichkeeps them present in our daily lives. They invariably bite their hosts and suck the blood that circulates through their skin.

64 INSECTS INVERTEBRATES 65

PreparationWithin tenths of a second, the fleaprepares itself to jump. It compressesthe resilin and at the same timecontracts its back legs. The back legshave a system of pads that retainthe tension and accumulate energy.

1

Key System

ActionThe flea accumulates energy bytensing the muscles of the thoraxand legs. When the accumulatedelastic energy reaches a certainlevel, the flea releases its legs. Asa result the legs generate asudden movement that causesthe flea to jump.

2 In FlightA flea can leap 24 inches (60 cm) at onebound. Its body is protected by armor-like overlapping plates that make up itsexoskeleton. During a series of jumps,fleas can fall on their backs or headswithout being injured.

3

HUMAN FLEAPulex irritansusually feeds onhuman blood.Unlike other fleas,they do not remainon the host.

DOG FLEASCtenocephalidescanisThis species isresponsible for90 percent offlea infestationsin dogs.

FLEAS IN THE HOMEFleas are very commonon dogs and cats.Fleabites generateserious discomfortfor domesticanimals becausescratchingirritates andinjures their skin.

WITHOUT EATING.

FLEAS CAN SURVIVE

3 months

FLEA VS. MANA flea jumps adistance equivalentto 200 times thelength of its body. Toequal this feat, aman would have tojump over a 130-story building.

THE DISTANCE A FLEA CAN JUMPIN TERMS OF BODY LENGTH

200times

LARVA

PUPA

ADULTFLEA

EGGS

TOTAL CHANGEFleas are holometa-bolous; that is, theirtypical lifestyle includes a completemetamorphosis.

The muscles in the coxa contract,generating enormous tension. Theresistance to the tension is supported bythe exoskeleton.

1

Once the jump is started, within thousandthsof a second the direction, intensity, andorientation of the jump are all established bythe torque that the muscles and leg segmentscreate for the flea to complete its jump.

2

On injecting theirstylet, fleas expel a

substance that irritates thehost but helps the fleas bykeeping the blood fromclotting while they aresucking it.

2The frontlegs are

important forfeeding. They holdthe insect in placeas it prepares tobite.

1

JUMPING LEGThe legs are furnishedwith extra uppersegments. Thesesupplements allow itto jump with speed.

INVERTEBRATES 6766 INSECTS

One of the most basic adaptations of insects hasbeen their ability to fly. Most have two pairs ofwings. Beetles (order Coleoptera) use one pair to

fly and one pair for protection. For example, the roundedbody of a ladybug or ladybird is nothing more than thecovering for a very sophisticated flight system. Itmakes these small beetles, which are harmless tohumans, great hunters in the insect world.

The Art of Flying Most insect species, from dragonflies tobutterflies, have two pairs of wings. Flies andmosquitoes are among the few exceptions.

A QUESTION OF NUMBER

“Ladies” of Land and AirSome 4,500 species of these beetles live throughout theworld. Almost all are brightly colored, with black spots on a

red, yellow, or orange background. These colors warn awaypredators, who usually associate bright colors with poison. In fact,some ladybugs are actually poisonous for small predators, such aslizards and small birds. Ladybugs pose the greatest danger toagricultural pests such as plant lice and gadflies, so they are oftenused as a natural biological pest control.

PreparationThe elytra can separate fromthe rest of the body. Theyprotect the thorax, and also thewings when folded inside.

1

TakeoffAlthough the colorful elytraare not used in flying, theinsect needs to lift them inorder to unfold its wings,which are seen onlyduring flight.

2

FlightWith the elytra open andspread like airplane wings,the second pair of wings isfree to move. The musclesat their base control thedirection of flight.

3

LandingThe insect reduces its flight speed. With itswings outstretched, it settles down to touchthe surface without gliding. Its hind legshelp it to stay balanced.

4

BODY ARMORThe elytra are brought closeto the body. Then the wingsare folded underneath.

AVERAGE SPEED OF FLIGHT

40-80 inchesper second

(1-2 m/s)

Adaliabipunctata

Coccinellaseptempunctata

Chilocorusstigma

Coleomegillamaculata

ON THE FLOWERor on the stalks of aplant is where theladybug finds theaphids it feeds on.

WINGSSeen only atnight, they foldalong a joint inthe middle.

Both pairs can stayflexed until the beetletouches down.

2 FRONT LEGS

remain extendedfrom takeoff.

1 HIND LEGS

SUPPORT FROMTHE LEGS

HEAD

THORAX

ABDOMEN

2 wingsFLY BUTTERFLY

BEETLES

CICADAS (ORDER HOMOPTERA)

4 wings

2 hard elytra2 wings

2 semi-hard elytra

2 wings

Wing

Thorax

The vertical muscle contractsand the wings move upward.

The horizontal muscle contractsand the wings move downward.

IDENTIFYING SPOTS

WING

7 blackspots

Raisedelytra

Name of the modifiedfront wing of beetles

ELYTRON

Raisedelytron

Visiblewing

Wingspreparedfor flight

FRONT VIEWOF ELYTRA

BACK VIEW

The insect isbetween 0.04 and0.4 inch (0.1-1cm) long.

SEVEN-SPOTTEDLADYBUGCoccinella septempunctataThanks to their help indestroying pests, duringthe Middle Ages thesebeetles were consideredinstruments of divineintervention from theVirgin Mary.

OTHER FUNCTIONSBeetles and otherinsects have two pairsof wings, but withdistinct functions.

APOSEMATISM The opposite ofmimetism: these insectsuse their bright colorsto scare away danger.

INVERTEBRATES 6968 INSECTS

For some insects, such as pond skaters in freshwater, or halobates in saltwater, the biblical feat ofwalking on water is no miracle, but an everyday task. When the waters are calm, the water insectknown as a pond skater uses the surface tension of liquid (and certain anatomical features of its

body) to do honor to another one of its names: “water strider.” But because they need air to breathe,any movement on the surface sends them skittering back to land. Other species have gone further

and become divers and swimmers, with mechanisms for breathing and moving underwater.

Diving, Swimming, and Skating

UnderwaterThere are several aquatic beetlespecies, with two basic

adaptations: the hind legs, in pushingthe beetle forward, work like oars,presenting a greater surface area whenmoving backward than forward, andthe elytra can trap air as a reserve forbreathing underwater. These speciesare among the major predators instagnant freshwaterenvironments. The divingbeetle measures about 1.4inches (3.5 cm) long.

THE SURFACE TENSIONCAN WITHSTAND

15times theinsect's

totalweight.

WATER STRIDERNeogerris hesioneThis species lives onfreshwater surfaces. Itmeasures 0.5 inch (1.3 cm) long.

FRONT LEGSare shorter than otherpairs. They are used fortrapping prey.

SURFACE TENSIONThe mutual pressure

among molecules of liquid

brings the molecules

together so that they

resist pressure that would

penetrate the surface.

5 feetper second

(1.5 m/s)

DIVING BEETLEDytiscus marginalis

Moving forwarddecreases thesurface area.

Moving backwardincreases the area.

It rises to thesurface to fill theair chamber.

WALKING ON WATERThe legs are arranged on the surface of the liquid in such a

way as to make it an elastic film. The hind legs use this

property for support and traction. Also, the insect supports

itself on segments of its legs, not on just one point.

SWIMMING LEGSA system of bristlesvaries the amount ofsurface in contact withthe water.

MIDDLE LEGSUsed as skatesto glide alongthe water

HIND LEGSprovide force to slidealong the surface.

CABEZA

THORAX

ABDOMEN

ANTENNA

x

LEGEND

Points of supporton the water

The middle and hind legsgrow fromseparate pointson the body.

The middlepair of legsis longer.

SHORTFRONT LEG

On the WaterUntil recently, it was believed thatinsects of the family Gerridae

skated on lagoons and ponds using atype of wax secreted by their legs. Laterit was discovered that their feet havelarge numbers of micro-hairs, 30 timesfiner than a human hair, that trap tinyair bubbles. The trapped air forms acushion that keeps their feet fromgetting wet, and if the feet begin to sinkthey are buoyed to the surface.

AIR

WATER

Each molecule exertspressure in all directions.

The angle of contactbetween the insect's footand the water is 167°.

Insects of the orderHeteroptera have dividedwings (hemielytra), with onehalf that is hard and theother membranous.

AIR

WATER

1

2

3

4

5

6

Chamber underthe elytra

Insect's body

AVERAGE SWIMMINGSPEED

Metamorphosis is the change in shape that insects undergo as they grow.There are two types of transformations: complete, like that of monarchbutterflies, and incomplete, like that of dragonflies or grasshoppers. Insects

with complete metamorphosis pass through an immobile state (called the pupal, orchrysalid, phase) in which their body is transformed by hormones within a cocoon.

Metamorphosis

70 INSECTS

Third shedding

Second shedding

Fourthshedding

Changeto pupalphase

1 In the Beginning, the EggThe adult female lays eggs among the leaves, where they will beprotected. Monarch butterfly eggs have colors ranging fromgrayish-white to cream, and they are shaped like barrels, 0.1 inch(2 mm) in diameter. The larvae grow inside the egg until theyhatch; after hatching, they eat the shell. 7 days

FIVE CHANGESWhen it hatches, the insect is shaped like aworm. This caterpillar will molt its exoskeletonfive times as it grows in size. Its internalstructure will not change, however. Each newexoskeleton is larger than the one before.

AMOUNT OF TIME THE LARVALIVES INSIDE THE EGGMATING AND EGG LAYING

When monarch butterflies mate, theystay joined all afternoon and evening,until the next morning, for a total of 16hours. After their first mating, thefemales lay eggs.

Hatching from the eggThe exoskeleton hardens. As theinsect grows, the exoskeletonbecomes too small. Eventually itsplits and falls off.

Simple MetamorphosisAlso called incomplete metamorphosis, because, unlikecomplete metamorphosis, it does not include a pupal

phase. The wings and legs develop gradually, so that theinsect does not need to spend a certain amount of timeimmobile. Locusts, cockroaches, termites, and dragonflieshave this type of metamorphosis. From an evolutionarystandpoint, it corresponds to ancient or primitive insects.One of its characteristics is the nymph stage of younginsects. The nymph gradually changes in shape as it grows.When it sheds its exoskeleton, the adult emerges. 1 2

3

EGG NYMPH

IMAGO (ADULT)

EMPERORDRAGONFLY

Anax imperator

2Larva orcaterpillari

makes its entry into the world byeating its shell. From then on, eating and

growing will be its main activities. Every time itsheds its skin, the old exoskeleton is broken. Theinsect forms a new, soft exoskeleton, which isgradually expanded by blood pressure. The

exoskeleton then undergoes a chemicalreaction that hardens it.

A SIMPLE ASSIGNMENTIn the caterpillar phase, the insect focusessolely on eating leaves. In this way itaccumulates the necessary energy for thephysiological processes of metamorphosis. Fordigesting the leaves, the caterpillar has a verysimple digestive track.

PREPARATION FOR THE PUPAL PHASEBefore passing to the next stage, the larvastops eating and eliminates any food leftin its digestive tract. The juvenile hormone,which keeps the transformation of thebody in check, starts to become inhibited.

3 weeks

CREMASTERThe caterpillar secretesa fibrous cushion thatsticks to the stalk of aplant. It hangs from thecushion with hooks onthe end of its abdomen.

FAREWELL TO THE OLD BODYThe larva's lastexoskeleton begins tofall off and is replacedby a greenish tissuethat will form thecocoon, or chrysalis.

INTESTINE

IS THE AMOUNT OF TIMETHE INSECT LIVES IN THELARVAL STAGE.

HANGING ANDIMMOBILETo leave the larvalstage behind andbecome a pupa, thecaterpillar quietlyawaits thetransformation.

EXOSKELETONCrossed with yellow, black,and white stripes, it is softafter every shedding andlater hardens. The insectalways emerges head first.

INVERTEBRATES 71

INSIDE THE LARVAThe insect's heart, nervoussystem, and breathingsystem are almostcompletely developedduring the larval stage,and they change very littleafterward. Thereproductive system isformed later.

ELIMINATING WASTESWhile emerging, the butterflysecretes a fluid containing thewaste produced during thechrysalis phase. This fluid,called meconium, is consideredrather foul-smelling.

CAMOUFLAGEThe chrysalid capsule hasshapes, textures, and colorsthat help keep it from beingnoticed, to protect it frompredators. The capsulestypically resemble leaves orbird droppings.

UPS AND DOWNS OF LIFE AS AN ADULTMating, reproducing, and laying tinyeggs to give rise to new generationswill be the main activities of the adultinsect. Each female lays an average of100-300 eggs during her life.

FLY AWAY, BUTTERFLYThe lifespan of this insect in its adultphase will depend on its luck, itsmigrations, and the attacks ofpredators . . .

3Pupa (chrysalis)i

After getting rid of its larval exoskeleton, the insecthangs immobile from a branch, protected by acocoon. Inside, it will develop its distinctive butterflyform. Although it does not eat during this period, itis intensely active biologically and undergoesconsiderable change. Histolysis, a process in whichthe larva's structures are transformed into thematerial that the insect will use to develop adultstructures, takes place at this time.

15 days 4 AdultAfter reaching its final shape, the butterfly will not grow any more. When the butterfly emerges from its cocoon, itswings are still wrinkled and damp. It will need to hang upsidedown to stretch them out to dry, so that they will be useful forflying. This will take several hours of waiting and struggling.From then on, the butterfly will feed on nectar.

from 5 to7 weeks

INVERTEBRATES 73

YOUNG ADULTOnce free of its covering, theadult is usually pale in color,and its wings are soft andfolded. After about 40 minutesthe wings expand, harden, andtake on their full color.

HORMONES IN FULLSWINGMetamorphosis is governed bythree hormones. One is thecerebral (brain) hormone, whichstimulates the prothoracicgland. This gland produces themolting hormone ecdysone,which causes the loss of the oldskin. The third hormone is thejuvenile hormone, which slowsdown the transformation to theadult stage.

TRANSFORMATIONS OF THE FLYThis side diagram shows thechanges in the organs of a fruitfly (Drosophila sp.) from the pupastage to the adult stage. Thecuticle of the last larval stageprotects the pupa. Thistransparent membrane allows thewings, the antennae, and thefolded legs to be seen while theyare forming. The pupa already hasthe dimensions of the adult flyinginsect, and it will not grow anybigger during the rest of its life.

BUTTERFLY SHAPEThe adult butterfly's wings and legsdevelop from the cuticle, or skin tissue,which is composed mostly of chitin.Other organs are preserved or rebuiltfrom regenerative cells.

JOINED, BUT NOT FOREVERAfter leaving the chrysalis,monarch butterflies from the samelitter stay together for a period ofthree to eight days before they gotheir separate ways.

BREAKING FREETo permit the butterfly toemerge, the mature capsulesplits along its length. Theinsect gradually stretches itsnew body and activates thecirculation of the hemolymph.

LENGTH OF THE PUPA,OR CHRYSALIS, PHASE

72 INSECTS

HISTOGENESISNew tissues are generated from hemolymph(the equivalent of blood), the Malpighiantubules (the energy-producing organ ininsects), and histolyzed tissue, including thelarva's muscles. The monarch butterfly pupa iscalled a chrysalis because of the color andstructure of the capsule that protects it. It isoval-shaped with gold and black spots.

WITHIN SIGHTAs the time draws near forthe adult to emerge, thechrysalis becomes thinner,changes color, and becomestransparent. Thetransformed insect can beseen inside.

Antennae

Mouth

Eyes

Legs

Wings

Reproductiveorgans

INTERNAL ORGANSInside the chrysalis, theinsect's body is changing intothat of an adult. The intestinerolls into a spiral shape toassimilate liquid food, and thereproductive organs aredeveloping for the adult stage.

INTESTINE

LEGSAgileand thin

ANTENNAEperceive odorsand transmitmessages.

EYEScan see only afew inches.

JAWSWeapons forattack anddefense

LEGSAlthough the legslack muscles, they are very strong.

METAMORPHOSISIn the egg stage, the future ant remains near thequeen but leaves her during the larval stage. Otherants then take care of the larva, and it will become anymph and form a cocoon to cover itself.

COMMUNICATIONAn ant communicates with its antennaethrough chemical means, by capturingparticles of certain substances(pheromones) that enable it to recognizeanother ant from the same colony. Antsdo not have a well-developed sense forperceiving sound.

INTERCHANGE OF FOODHaving two stomachs, an ant can share food. Thetransfer begins when the receiving ant uses its frontlegs to touch the lip of the donor ant.

VENOM may contain formic acid and can kill or paralyze the prey. It comes fromspecial glands in the lower abdomen.

JAWThe jaw is the ant'smain weapon ofdefense, with a bitethat can scare away orharm a rival. The jaw isalso used for huntingand feeding.

10,000ANT SPECIES.

THERE ARE ABOUT

QUEENANT

Americanfarmer ant

Clampingjaw

EGGS LARVAE NYMPHS COCOON

AbdomenPoison sac

Poisonousstinger

Stream ofpoison

YOUNG ANTS

VELVETYTREE ANTLiometopumoccidentale

LARVAEare carried to anotherchamber to grow.

2

NYMPHSare fed and taken careof in another area.

3

EGGSare laid by the queenin the lowest area.

1

COCOONSThe new ants hatchready to work.

4

CropSocial pouch

StomachIndividualpouch

Four wings

Two wings

Foodreserves inabdomen

Storage

FeedingAnts cannot eat solid food. The plants and animalsthey eat are mixed with saliva to form a paste,which is used to feed the whole colony.

The CastesEach ant plays a role in the nest and isassigned its role at birth. Drone, soldier,worker, and replete worker (which storesfood reserves) are the castes that distinguishwhat chores each ant will have.

The AnthillAfter mating, the queen loses her wings andchooses a place to lay eggs. At first she lives onreserves derived from the muscle mass of herwings and some of the first eggs she has laid.She takes charge of raising the first generationof worker ants, which will then take care offinding food while the queen focuses exclusivelyon laying eggs.

DefenseThe most widely used defense is biting and spraying streams of formic acid.Soldier ants have the job of scaring away the enemy because they have largerheads than worker ants.

SOUTHERN WOOD ANTFormica rufa

REPLETEANTS

TRAP-JAWANTOdontomachusbauri

Ants are one of the insects with the highest social organization. Inthe anthill, each inhabitant has a job to do. The head of the family isthe queen, the only one that reproduces. All the rest of the ants are

her offspring. During mating, queens and drones (males) from variouscolonies mate on the wing. The queens need to mate several times, because the sperm they receive will have to last their lifetime.

INVERTEBRATES 75

Antennae

Abdomen

Legs

Petiole

Thorax

HeadEyes

BLACK GARDEN ANTLasius niger

QUEENThe largest ant. She lays the eggs that will becomeworkers, drones, and new queens.

DRONEHis only function is mating; afterward he dies.

WORKERThe worker ant mayhave the role ofgathering food,cleaning, orprotecting the anthill.

Order and Progress

FOOD STORAGEHoneypot antscoordinate thefood supply.

MAINENTRANCE

UNUSED TUNNELwill be reopened whenthe anthill gets too hot.

UNUSEDTUNNEL

74 INSECTS

76 INSECTS

Goal: SurvivalE

volution has molded some striking traits into living beings. In particular,some insects, disguised as branches or leaves, can escape notice so as tohunt or to hide from predators. To avoid being attacked, other insects

develop colors and shapes that deceive other animals and keep them fromattacking. Hiding and showing off are two opposite strategies thathave been favoring the survival of the fittest for millions of years.

INVERTEBRATES 77

Masters of SimulationCamouflage, or crypsis, is a phenomenonin which animals use amazing disguises

as advantageous adaptations. Camouflage isused both by hunters and by potential prey.Insects' bodies may be disguised as varioussubstrates and parts of trees, such as bark,leaves, and branches. These maskingtechniques are a convenient way for theinsect to fade into the background.

The most widely imitated insectsare ants, bees, and wasps, becausethey produce toxic substances thatcan be deadly.

Defense

THISTLE MANTISBlepharopsis mendicaThese mantises usecamouflage to huntunsuspecting insects thatget too close to theirpowerful front legs.

BRIMSTONE BUTTERFLYGonepteryx sp.The profile of the wingsresembles the shape of cut leaves.

FRONT LEGSmove slowly sothat the preywill not detectthem.

VEINSIn an extraordinarysimulation, the veins look like the veins of leaves.

EYESCompound; enablethem to monitortheir environment

DOUBLE PROTECTIONCaligo sp.Owl butterflies combine Batesianand Mullerian mimicry. Predatorscan confuse the owl butterflywith leaves, but if a predatorsucceeds in finding it, thebutterfly folds its wings to looklike the shape and eyes of anowl. The predator, confused,backs off from attacking.

PEACOCK BUTTERFLYInachis io

The flashy, aposematic(warning) coloration

keeps predatorsaway by warning

of the dangerthe insectposes.

These insects use survival strategiesdesigned to keep predators fromseeing them. This disguise is theironly means of defense.

DisguiseAUSTRALIAN STICKINSECTExtatosoma sp.This stick-like insectsways back and forth asif tossed by the wind.

LEGS imitate twigswith dryleaves.

BODYBranch-shapedabdomen

WINGS These wings look likeleaves, with a similarcolor, shape, andstructure.

FALSE EYEThe scales arepigmented to look

like eyes.

Warning SignalsMimetism is the imitation ofcharacteristics belonging to

dangerous or bad-tasting animals.Replicating the colors and shapes ofdangerous animals is known as Batesianmimicry. On the other hand, if an insectproduces foul-smelling substances todisgust the predator, that is calledMullerian mimicry.

INVERTEBRATES 7978 INSECTS

The biological relationships between speciescan have both positive and negative consequences.One relationship that has good results is mutualism, a

relationship between species in which the organisms benefit each other. Forexample, ants and aphids (plant lice) have established a beneficial interaction. Ants defend and nurture the development of aphid colonies on a plant. In return,

the aphids provide a sugary substance to feed their protectors.

Chain ReactionThe beneficial interaction between aphidsand ants can produce secondary effects.

In some cases, plants benefit indirectly from thepresence of aphid-protecting ants. Theseguardian insects drive away the herbivores thatfeed on the tender leaves. In this way, plantsinvest less energy to replenish theirphotosynthesizing organs.

BLACK GARDEN ANTLasius nigeris between 0.1 and 0.2inch (3 to 5 mm) long.The thorax is fused to thefirst abdominal segment.

BLACK BEAN APHIDAphis fabaeis between 0.05 and0.1 inch (1.5 to 3 mm)long. It has very short antennae.

SugarCurrents Generally, aphids form coloniesthat live on a single plant.They usually place themselveson the underside of a leaf,where the aphids can reachthe leaf's veins. The veinscarry sugars from the leavesto the remainder of the plant,and the aphids use this flow ofsugar as a source of food.

HONEYDEWis a secretion with ahigh concentrationof simple sugars.

ARE EXTRACTED FROM A COLONY OF APHIDSBY ANTS EVERY YEAR.

2,200 pounds(1,000 kg)

of honeydew

DROP OFHONEYDEW

ANTIts antennae caress theabdomen of the aphids andstimulate sugar secretion.

APHID

APHIDExtracts nutrients from the leave's ribswith its stylet

Horn-shapedappendages

Rectum

Anus

StomachAntennae

Vein ofthe leaf

LEAF

Stylets

Caudal

Salivarygland

PARTNERSSugars are the product thatlinks these insects.

One for You,One for Me ...

KEPT IN RESERVEAphids need protection frompredators, such as butterflylarvae. Ants pick up eggs andnymphs in their jaws and carrythem into their anthills, out ofthe reach of any predator.

Relationship with People

Apiculture, or keeping bees touse their products, is a veryold practice. Originally,people only hunted beehives.Not only did they eat the

honey from the beehives; they alsomixed it with water and left it toferment so they could make alcoholicdrinks. Today the production of honeyhas been perfected in such a way that

other products, such as pollen, royaljelly, and propolis, or bee glue, are alsoobtained from the hive. Just as useful asbees, leeches have always been used astherapeutic tools to soothe headaches

and stomach upsets. In this chapter youwill also learn what happens wheninsects such as locusts reproduce atdangerous rates.

HUNGRY TOGETHER 88-89

BENEFICIAL VAMPIRES 90-91

THE NEVER-EMPTY HOME 82-83

AFLOAT WITH DUST 84-85

BEEKEEPING 86-87

THE HIVE Movable frames allow thebeekeeper to remove a framewith young bees and in this waystart a new colony.

INVERTEBRATES 83

In the GardenThe home garden is a natural environment in whichfood chains become established. Species such as snails,which feed on plants, can be destructive. Butcarnivorous species can keep harmful species at bay.Earthworms and some beetles serve as environmentalcleaners because of their eating habits.

In the RoofThe wood in roof beams and spacesbetween them forms a uniqueenvironment within a house, especiallyfor the insect order Hymenoptera.Likewise, several species of beetlesfeed on wood and lay their eggs in it.

RUERuta graveolensSoaked in waterthis plant repelsinsects.

The home can be another place colonized by invertebrates. Some arrive seeking humidity,shelter, or food; others are attracted by the scent of skin, wool garments, or woodenceilings. Generally, they are considered a threat and are fought, but some can be truly

beneficial. There are insects, for instance, that can act as a plague control in the garden.Various strategies can help keep some “ecologic balance” in the home.

“Magic” CarpetKeeping carpets clean within the home is critical,because few are the insect species that live in acarpet and are nice to humans.

TERMITESNasutitermes sp.Live inside the woodthey feed on.

THYMEThymus vulgarisThis herb attractspollinating bees andrepels flies.

BLOODSUCKING BUG(TRIATOMINE)

SPIDERSTheir presence indicatesthat there are many insectsin the house.

ORIENTAL COCKROACHBlatta orientalis

BLOODSUCKING BUG(TRIATOMINE)Triatoma infestansTriatoma transmits Chagas disease tohumans. Chagas disease producescardiac, digestive, nervous, andrespiratory complications. WhenTriatoma bites a human, it excreteswaste on the skin that can containthe parasite Tripanosoma cruzi. Theparasite then enters the bloodstreamwhen the victim scratches the bite.This insect lives mainly in makeshiftdwellings, between thatched roofsand unbaked bricks.

TO CONTROL PLAGUESMany plants, alone or in combinationwith other plants, are effective andselective.

Plagues and IllnessWhen the females feed on human blood, mosquitoes (suchas those belonging to the family Anopheles, bearers ofmalaria) and other insects become vectors for illnesses,since they can transfer microscopic parasites to people. Forthis reason, bodies of stagnant water, which is wheremosquito larvae develop, should be avoided.

AUGER BEETLESXylopsocus sp.The adult beetle lays eggs, andthe larva burrows into wood,creating tunnels 0.25 inch (0.6cm) wide in the wood.

HOUSE DUST MITESDermatophagoides farinaeSome dust mites carry parasites;others cause allergic reactions.

FLEASCtenocephalides sp.

BURYING BEETLENicrophorus sp.

PILL BUGArmadillidiumvulgare

SPINY-HEADEDWORMPhylumAcanthocephala

LADYBUGCoccinellaseptempunctataeats fleas and gnats.

LARVAE

MOSQUITOAedes aegyptiis the vector for yellowfever and dengue fever.

SNAILHelix aspersais a nightmare forthe green leaves inthe garden.

BLACK ANTSLasius nigercan go from their nest tothe interior of the house.

EARTHWORMLumbricus sp.

LAVENDERLavandula angustifoliarepels ants (10 ounces in aquart [300 g in about 1 l]of boiled water).

65 infectiousillnesses.

FLIES CARRY AT LEAST

WASPSApis melliferabuild their nests(hives) under theeaves.

At NightSome “inhabitants” of the house avoid daylight and prefer the cover ofdarkness so they can go unnoticed bypeople or predators.

CENTIPEDES

COCKROACHES

A COLONY OF 60,000TERMITES CAN EAT

2 ounces(5 g) OF WOOD PER DAY.

The Never-Empty Home

82 RELATIONSHIP WITH PEOPLE

INVERTEBRATES 85

Afloat with DustD

ust mites are minuscule arachnids that move among dustparticles searching for food. The larvae of the smallestspecies barely reach .004 inch (100 microns). Ticks are

larger and can reach .5 inch (1 cm) in length. Their body is full of grooves that absorb humidity, and their life spans fluctuatebetween three and four months. They adapt to almost anyhabitat: marine, freshwater, or land.

Dust mites are part of the oldest, mostvaried, and largest group of animals that

have existed since life appeared on the planet-thearthropods-and, within the arthropods, thearachnids. Their body form is highly varied.Contributing to this variety is the arrangementand appearance of their legs and hairs. They canhave a thin, elongated body or a short, wide body;

their bodies can also be oval, round, cone-shaped,or rhombus-shaped, and the colors depend on thespecies. There are green, red, violet, orange, andeven transparent mites. These insects aredistributed throughout the world, and they haveadapted to every environment: they live on theground, in plants, in storage products, in thewater, and in the skin of animals.

Small, They are Found Everywhere

0.10-0.25inch (3-6 mm)

The tick is the largest acarid; its body has nodivisions, and it feeds on the blood of itshosts. It is generally found among tall grassesor in plant leaves, waiting to hook onto anyanimal or person that passes by. When a ticksucceeds in doing so, it uses a hook-likestructure in its mouth to penetrate the skinand to begin to suck blood. Once its bodyswells with blood, the tick lets go.

TICK2

The Sarcoptes scabei is a tiny mite that livesunder the corneal layer of the epidermis inpassages that the female makes in the skin, whereshe lays her eggs. Between 10 and 14 days laterthese eggs become adult sarcoptes mites. The

presence of this mite under the skin producesintense itching, which can be severe and whichcan worsen at night. There are special creams andlotions to treat this infection. If boils appear, theinfections must be treated with antibiotics.

SARCOPTES MITE1

House dust mites are so tiny that up to 5,000 of the animals can live injust one grain of dust. Their characteristics include a bulky body, eightshort legs, and short sensory hairs. They have appendages next to theirmouth that they use to tear or bite and, to their side, pincers with whichthey hold objects. The body is almost monolithic, practically withoutdifferentiation among its parts. Even though dust mites do not bite andare themselves harmless, their eggs and feces cause severe symptoms inpeople who are allergic to them.

DUST MONSTERS3

Liquid FoodWhen they come in contact withwhat will be their food, dustmites secrete digestive juices thatsoften and liquefy solids becausetheir mouth or ingestion systemlets them ingest only liquid food.

HumidityA fact that many people are not aware of is thatthe presence of mites is closely linked to humidity.These minuscule animals can cause severe harmat home. They can cause many respiratoryillnesses, including asthma. Because dust mitesneed humid conditions in order to live, everyroom should be well-ventilated.

Flying WasteMatterThe microscopic fragments of fecalmatter of the dust mite are carriedthrough the air very easily, blendingwith dust particles. In this way theyare transported for great distances,and they are one of the mostcommon causes of allergic reactions.

Favorite PlacesHouse dust is a conglomeration of small, suspendedparticles. The content of household dust varies from hometo home, and it depends on, among other things,construction materials used and the presence of domestic

animals. A dust particle can contain fibrous material, skinscales, animal hair, bacteria, mold, and other natural orsynthetic materials. Mites can live among such particlesbecause they feed off those materials.

MOUTHPIECESIn these bugs themouthpieces are in a smallfront projection, thecapitulum (gnathosoma),formed by the appendagesthat surround the mouth.On each side there is achelicera that tears,crushes, or bites the food.

HAIRScome out of the mites'legs. These are actuallysensory organs.

DUST MITE Each of its legs has six parts. Itdoes not fly; the air carries it.

CUTICLEEven though it is solid

and flexible, it mustbe kept humid.

0.001 inch(0.2 mm)

84 RELATIONSHIP WITH PEOPLE

Mechanical centrifugestypically rotate at 200 rpm.

THE SUITMade of a thick andgenerally white material.The ventilations are made of double plasticmaterial in both front and back.

From 25 to 50 pounds(11 to 23 kg) of honeyare obtained fromeach super.

86 RELATIONSHIP WITH PEOPLE

BeekeepingT

he bee is the only insect that humans have kept fromantiquity for their own benefit. Thanks tobeekeeping, people have been able to

collect the honey that bees produce. Honeywas the most widely used sweetener inEurope and Asia until the spread ofsugarcane during the Middle Ages. Withthe introduction of new techniques, modernapiculture also obtains pollen, propolis, and royaljelly from bees. Shown here are some details ofthe basic components of a beehive.

FLOORBase ofthe hive

BOTTOM BOARDThis part is placed at aheight that will protectthe hive from ants orfrogs.

BROOD CHAMBERThis structure isgenerally located inthe bottom part ofthe hive.Their cells includelarvae.

QUEENSEPARATORWorker bees canpass through theseparator, but thequeen, which islarger, cannot. As aresult, honey isstored throughoutthe hive, but eggsand young bees arefound only in thebottom section ofthe hive.

SUPER is the name given toeach detachablemodule. The upper onesare the sugar supers,and the lower ones areused to raise the young.

Open cellswith honey

Closed cellscontaininglarvae

The queen lays her eggsby moving in a spiral-shaped pattern.

LOFTThis space acts as anair chamber andprevents the sugarsuper from coming intocontact with theexterior.

ROOFThe upper surface of the

hive can be made ofwood or wood

panels.

MOVABLE FRAMESEach super has about 10movable frames that areattached to a burr combwith a hexagonalpattern.

Nature's EngineeringHoney is one of the substances that the bees themselves eat. Thebees make honey out of flower nectar and pollen from the green

parts of plants. They carry the pollen to the hive as a source of proteinand use propolin, a tree resin, as a form of antibiotic. Apiculture seeks topromote natural production processes in order to make use of thesesubstances for human benefit.

1

2

3 5

6

4

Honey Collection

The SmokeApplied by means of a smoke-producingmechanism, it scares the bees and causesthem to eat honey, reducing their tendency tofly and sting.

Extraction of the FramesThe movable frame system allows for frame removalwithout affecting the young brood, and the frames canbe used again. Before Langstroth's invention, theseframes were fixed in place.

The Centrifugeis a machine that rotates. The honeyis heated to a temperature thatliquefies it. It is drained from theframes and separated from the wax.

Filtering and BottlingThe honey is stored in steel tanks for a week and up to a month toallow any impurities to separate.Bottling and storage require anenvironment that is dry to preventthe honey from absorbing moistureand that is free of any odors, whichmight contaminate the honey.

bees live in atypical hive.

30,000

INVERTEBRATES 87

The Bee's WorkWorker bees, the real workers of the hive, carry out theirduties from the minute they are born: they build and maintainthe cells, feed the larvae and the queen, and clean and protectthe hive. Outside the hive, they are in charge of collectingflower pollen and nectar.

THE ARTIFICIAL HIVEhas movable panels and frames that permit extraction of thehive's products without destroying the bee colony. This systemwas invented in 1851 by Langstroth, an American.

NECTARThe bee takes the nectarfrom the flower, ingests it,mixes it with its saliva, andtransports it to the hive.

OPENINGat the bottom of the hive allows worker bees to enterthe beehive chamber where the young are raised. It islocated between the floor and the first super.

HONEYREGURGITATIONThe bees deposithoney in all of thecells of the hive.

BROOD FRAMEIs the part of the hiveused for beereproduction. Here iswhere the queen laysher eggs.

The beekeeper chooses a super, removes it from thehive, and takes out the movable frames by hand. Tohandle these frames, the beekeeper uses a special suitand other equipment to protect against bee stings. Thehoney is removed from the detachable frames in acentrifuge, and the frames are then put back into the hive.

The frames havea wireconstruction.

The frames areseparated from eachother by about 0.2 inch(6 mm), the distancebetween panels in anatural beehive.

Hat andmask witha grille

Boots

Some aretwo-piecesuits.

Smoker

60 pounds(25 kg) of honey

NECTAR, HONEY'S SOURCENectar is made up of 80 percent water and issecreted at the base of the flower's corolla.Honey's flavor depends partly on its aromaticcomposition, and the beekeeper can select theprincipal flowers that are the source of the nectarby changing the location of the hive.

IS STORED INSIDE A HIVE SO THEBEES CAN SURVIVE THE WINTER.

THE POPULATION OF THE HIVEIS KEPT STABLE AS LONG AS NOSUPERS ARE ADDED.

Queenbee

Workerbee

Centrifuge

THE CHOSEN ONESFlowers with a goodcontent of glucoseand protein.

SIGNALINGA worker bee findsa source of pollenand lets the rest ofthe hive know.

88 RELATIONSHIP WITH PEOPLE

Hungry TogetherU

nder specific environmental conditions, locusts reproduce very rapidly and forma swarm. In Africa, the Middle East, and India locust plagues destroy vegetationand produce great crop losses. Consequently, this type of plague represents a

great danger to agriculture and causes great economic loss, hunger, and illnesses inaffected populations. Chemical, physical, and biological methodsare used to repel the locusts, reducing the harmfuleffects of the invasion.

INVERTEBRATES 89

IS THE YEAR WHEN ALOCUST PLAGUE ATE ALLOF THE CROPS AND LEFT

CLOSE TO 100,000PEOPLE DEAD IN NORTH

AFRICA.

1931

OF VEGETABLES ARE WHAT AMEDIUM SWARM OF LOCUSTS,

FORMED BY 50 MILLIONINSECTS, EATS IN ONE DAY.

100 tons

Locust PlagueThe species that causes plagues of locusts onthe African continent is the desert locust,Schistocerca gregaria. This insect belongs to theAcrididae family and to the order Orthoptera.The locust has an elongated body, about 2 to 3inches (6-8 cm). The locust modifies its behaviorand appearance in response to environmentalconditions. It also feeds on most crops, on wildplants, and on some trees, such as sapwoods.

Pest Control The countries victimized by locusts defendthemselves by chemical or biological means on the landor from the air. Pesticide use is restricted, and pesticides canbe used against a swarm only when it has begun to form,because misapplication of a pesticide can affect other insectsand crops. The locusts are controlled by the application ofpoisonous bait and by plowing up the ground to bury the eggs.

When rainfall creates the appropriateconditions for their reproduction, locusts

that live in desert or semiarid regions multiply at adizzying rate. If the species is in the solitary phase,it is harmless, but when rains come and bringabout abundant plant life, the locusts gathertogether, increasing their reproductive capacity. At

that point the locusts mutate into their gregariousphase and change not only their movements butalso their morphology. Each female is capable oflaying 120 eggs, so that an area of 2.5 acres (1 ha)can breed up to 600 million locusts, which willgather into mile-long swarms that travel largedistances in search of food.

How Does the Plague Start?

SUMMER BREEDING ANDCONSECUTIVE MIGRATION ZONE

WINTER AND SPRING BREEDING ANDCONSECUTIVE MIGRATION ZONE

Locusts reproduce at a rate of millions at a time,and they devour all of the food that lies along theirpath. The map shows the two main summerbreeding zones.

The swarm of locusts moves to other zones in orderto reproduce and feed itself. Afterward, duringwinter and spring, the locusts retrace their path,and the cycle starts over again.

LOCUSTS INANTIQUITYThe devastating effectsof locusts can be tracedback thousands ofyears. Locusts wereknown as one of theseven plagues of Egypt.

90 RELATIONSHIP WITH PEOPLE

Beneficial VampiresL

eeches are worms that have been used as therapeutic tools forthousands of years. History relates that they were used as a remedy forheadaches, stomach complaints, eye diseases, mental illness, and other

conditions. As the use of drugs increased, the medicinal use of leeches wasgradually forgotten. In the 1980s, however, leeches once again began to beused in microsurgery and reconstructive surgery.

Lifesaving SalivaEvery time these worms bite a host,substances are mixed into their

saliva from glands in their mouth.Anticlotting components, vasodilators,and anesthetics have been identifiedamong these substances, which areextracted and used in clinical medicine.Researchers are also trying to fabricatesynthetic leech saliva through the use ofbioengineering techniques.

The use of leeches inmedicine goes back over

3,000 years. In Greece, Rome, andSyria these worms were used toremove blood from many areas ofthe body. It was believed thatbloodletting, or phlebotomy, could

cure anything from local pains toinflammation and mental disease. Inthe 18th and 19th centuries, leecheswere sold in European pharmacies,and they became very popular inthe therapies of the day, especiallyin France.

Ancient Uses

INVERTEBRATES 91

FRANÇOIS J.-V. BROUSSAIS(1772-1838) French doctor who believedthat most diseases werecaused by the inflammation ofthe intestines and whopreferred bleeding with leechesas a cure. His opinion becameso popular that in 1833 he had40 million medicinal leechesimported into France.

EUROPEANMEDICINAL LEECHThis leech is used inmedicine to treat thecongestion of veinsin reconstructive andplastic surgeries. Thebite causes ahemorrhage where thetissue graft is placed,imitating the circulationof the blood.

While feeding on blood, theleech secretes its ownanticlotting agents so that theblood will not spoil inside itsbody while waiting to bedigested. Its salivary glandsproduce hirudin, a specificthrombin inhibitor.

BLOOD CLOT

The leech has two suckers, one at itsfront end, where the mouth and jaw are

located, and another at the rear.

SUCKER

THE ONLY FARM IN THE WORLD THATSUPPLIES LEECHES IS LOCATED INWALES, IN THE UNITED KINGDOM. ITHAS MORE THAN 50,000 LEECHES THAT ARE SHIPPED TO LABORATORIES AND HOSPITALS IN 30 COUNTRIES.

BREEDING FARM

Illustration of a chapter of theDecameron by Boccaccio,which shows the use ofleeches to treat illnesses. The

patient is the Romanemperor Galerius, whohas a disease thatcauses the putrefaction

of the body. The threedoctors, aghast at

his condition,have put leecheson his body tocure him.

THE DECAMERON

Leeches are classified according to howthey feed. One group of leeches includesanimals whose pharynx has no teeth andcannot be turned outward. A second groupincludes leeches whose pharynx is toothlessbut can be turned outward like anelephant's trunk, projecting out of theleech's mouth, and can be inserted into thehost's soft tissues. The third group includeshighly specialized leeches in which thepharynx cannot be turned outward but isarmed with three chitinous jaws withserrated edges.

TYPES OF LEECHES

TEETH

MOUTH

With 300 teeth in its triple jaw,the leech cuts the victim's skinand sucks the blood with itspowerful pharynx and thesucker on its mouth. Betweenthe teeth it has glands thatsecrete hirudin, which keepsthe victim's blood from clotting.

HOW A LEECH TRAVELSAt either end of the leech is a cavity that theleech can use to attach itself to a surface. Tomove forward, it attaches one endon the ground and, with anundulating movement,draws the other endtoward it.

The segmented body of the leech allows it tomove with undulating movements when

necessary, for example, to walk. The leech canalso put on a show when it is on alert in the

presence of a host. At such times it managesto stand itself up on one of its ends.

The leech advances its frontend and attaches it to theunderlying surface. It thendraws its rear end forward.

1When its rear end reachesthe attached front end, theleech attaches the rear endto the underlying surface,and the sequence ofmotions is repeated.

2

2

There are 600 species of leeches.Leeches usually have 34 segments, butthey can have 17 or 31. They live mainly

in freshwater environments, but a fewlive in saltwater, and some have adaptedto life on land in warm, damp places.

LEECHES1

TWISTINGThe sections of theleech's body allow itto flex and assumedifferent postures.

ELASTIC BODY

Once the leech's mouth isplaced on the body, it begins tosuck blood at the rate of onecubic inch every 2 hours and40 minutes.

SUCKING MOUTH

THE MASS OF ITS BODY.

A LEECH CAN ABSORB ANAMOUNT OF BLOOD EQUAL TO

10times

50,000

92 GLOSSARY INVERTEBRATES 93

Glossary

AbdomenPosterior portion of the body of arthropodsconsisting of similarly formed segments,containing the reproductive organs and a partof the alimentary canal. In insects andarachnids, it is the posterior section of the body.

AdaptationA structural, physiological, or behavioral traitthat allows an organism to live in itsenvironment.

Ambulacral GrooveIn echinoderms, any of the radial groovesthrough which the hydraulic system's tube feetprotrude.

AnaerobeAn organism that can live without free oxygen.

AnnelidsAnimals with a long cylindrical body consistingof ring-formed segments.

AntennaeA pair of long sensory appendages on the headof many arthropods.

ArachnidAn eight-legged arthropod.

ArachnologistA scientist who studies arachnids-spiders andrelated groups.

ArthropodAn animal with articulated appendages and asegmented body, covered by an exoskeleton.

Asexual ReproductionAny reproductive process, such as theproduction of gemmae or the division of a cellor organism into two or more approximatelyequal parts, that does not involve gametesjoining together.

Bilateral SymmetryCorporal form whereby the right and lefthalves of an organism are approximate mirrorimages of each other.

BiologyThe science that studies living organisms-theirconstitution, structure, function, and relations.

BrachyopodsA group of marine invertebrates whose softbody is protected by a shell consisting of twoparts called valves.

CalciteA form of the chemical compound calciumcarbonate.

Carrion EatersAn animal that feeds on dead animals it finds.Given the occasion, some large carnivores suchas lions and hyenas can behave like carrioneaters.

CasteA social group that carries out specific tasks,characteristic of ants and bees, among otherinsects.

CelomaA cavity formed between layers of mesodermin which the alimentary tract and otherinternal organs are suspended.

CephalopodA class of exclusively marine mollusks withtentacles or legs attached to the head. Theseappendages have rows of suckers that areused for capturing prey and copulation.

CephalothoraxThe head and thorax combined in one singlebody segment.

CuticleAn organic, noncellular protective coveringsecreted by the epidermis.

DefecationThe part of an organism's digestive processthat consists of eliminating undigested matter.

DermisThe internal layer of the skin below theepidermis.

DeuterostomaAn animal in which the anus is formed in ornear the developing embryo's blastophorezone, and whose mouth is formed afterward inanother location; the echinoderms and thechordates are deuterostoma.

DimorphismOne species that exists in two distinct forms.

EchinodermsInvertebrate marine animals. The bodies ofthe adults have a pentagonal symmetry.Underneath the skin they have a calcareousskeleton with spines and protuberances.They have an internal hydraulic system,connected with ambulacral feet, that makeslocomotion possible.

EndemicNative to a particular geographical region andrestricted to it.

EndodermOne of the three layers of the embryonic tissueof animals; it originates in the epithelium thatcovers certain internal structures.

EpicuticleThe thin, outermost layer of the arthropodexoskeleton, consisting primarily of wax.

EpidermisThe outermost layer of cells.

Epithelial TissueType of tissue that surrounds a body orstructure or covers a cavity. Epithelial cellsform one or more regular layers with littleintercellular material.

EtologyThe comparative study of animal behavior inits natural habitat, and the evolutionary,genetic, ecological, and physiological factorsthat influence its manifestation.

EvolutionThe changes in the genetic reservoir from onegeneration to the next, as a consequence ofprocesses such as mutation or naturalselection, among other things.

ExoskeletonThe external covering supporting the body, co-mmonly found in arthropods. It is like an arti-culated shell made of chitin; it serves as a su-pport for muscles and the soft internal organs.

EyeletSimple light receptor, common amonginvertebrates.

FamilyA category in taxonomy that groups genustogether; lower than order and higher than genus.

FossilThe preserved remains of an organism thatdisappeared a long time ago.

GameteThe mature reproductive cell that combineswith a gamete of the opposite sex to form azygote that is usually diploid; male gametes are

called spermatozoids and female gametes arecalled ovules.

Gastrovascular CavityA digestive cavity with an opening,characteristic of the phyla Cnidaria andCtenophora. It has digestive and circulatoryfunctions.

GenusA category in taxonomy that groups speciestogether.

GeotropismA directional response to gravity.

GonoporeA pore in the reproductive apparatus throughwhich gametes pass.

HemocellA blood-filled cavity inside the tissues;characteristic of animals with an incompletecirculatory system, such as mollusks andarthropods.

HermaphroditeAn organism that has both reproductivesystems, male and female; hermaphroditesmay or may not self-fertilize.

HormoneAn organic molecule, secreted in smallamounts by one part of an organism, thatregulates the function of other tissue or organs.

HostAn organism in which a parasite lives.

Hydrostatic Skeleton A skeleton in which fluid is contained bymuscular walls that transfer the force fromone part of the body to another whensubjected to pressure.

CheliceraFirst pair of appendages in crabs, sea spiders,and arachnids, usually in the form of pincersor fangs.

ChitinTough, durable polysaccharide that containsnitrogen and is found in the exoskeleton ofarthropods or other surface structures of manyinvertebrates, and also in the cell walls of fungi.

ClassOne of the many divisions into which scientistsclassify animals. The invertebrates form aseparate class of their own.

ClassificationThe process of establishing, defining, andordering taxa within a hierarchical series ofgroups.

CocoonA protective sheath usually made of silk. Manyinsects make cocoons to protect themselvesduring the pupa stage, until they become adults.

ColonyA group of animals of the same species thatlive and work together to survive.

CommunityThe entire population of organisms that inhabitan environment in common and who interactwith one another.

Compound EyeIn arthropods, a complex eye made of manyseparate units, each of which has light-sensitivecells and a lens that can form an image.

CrustaceanAn animal of the arthropod group, withantennae and articulated appendages, thatuses gills to breathe and has a body protectedby a thick covering.

94 GLOSSARY INVERTEBRATES 95

InvasiveRelating to a species or organism that wasbrought into an environment and harmsbiodiversity, agricultural or fishingproductivity, or human health.

InvertebrateAnimal without a spinal column. Some, such asworms, have soft bodies. Others, such asarthropods, are protected by a hardexoskeleton.

KingdomTaxonomic category that includes phyla ordivisions. Until the appearance of the categoryof domain, the kingdom was the highest-levelcategory in biological classification.

LarvaAnimal in a developmental stage, after leavingthe egg. It can feed itself but has not yetacquired the shape and structure of the adultsof its species.

MandibleAppendage immediately below the antennae,used to trap, hold, bite, or chew food.

MantleIn mollusks, the outer layer of the body wall ora soft extension of it. It usually secretes a shell.

MediumElement or substrate where organisms live.

MesodermThe middle layer of the three layers ofembryonic tissue.

MetamorphosisAbrupt transition from the larval form to theadult form.

MetazoaMain group in the animal kingdom (includingmollusks, annelids, and arthropods) in whichthe mouth is formed at or near the blastula inthe developing embryo.

MicroorganismOrganism that can be seen only with amicroscope.

MigrationSeasonal travel of animals from one region toanother to reproduce or to seek food, betterclimate, or better living conditions in general.

MimetismProperty of certain animals and plants toresemble living things or inanimate objectsthat live nearby, mostly by means of color.

MolluskInvertebrates of the phylum Mollusca, with asoft body divided into a head, foot, and visceralmass. They have a fold called a mantle thatenvelops all or part of the body.

MoltingRemoval of all or part of the outer covering ofan organism; in arthropods, a periodicchanging of the exoskeleton that enables themto grow in size.

NutrientsChemical elements essential for life. Examplesare carbon, oxygen, nitrogen, sulfur,phosphorus, magnesium, and potassium.

OmmatidiumThe simple visual unit of a compound eye inarthropods; it contains light-sensitive cells anda lens that can form an image.

OmnivoreLiving being that feeds on plants and animals.

PredatorOrganism that feeds on other living beings.

PseudocoelomBody cavity consisting of a fluid-filled spacebetween the endoderm and the mesoderm,characteristic of nematode worms.

PseudopodTemporary cytoplasmic projection of anamoeboid cell whose movement and feedingoccur through phagocytosis.

Radial SymmetryThe regular disposition of body parts around acentral axis in such a way that any plane thatcuts through the axis divides the organism inhalves that constitute mirror images of eachother. It is seen in adult echinoderms.

Safety ThreadA silk thread that a spider leaves behind whenit is moving, attaching it from time to time tovarious surfaces.

SalinityMeasurement of the amount of common salt inwater or soil. Common salt is a sodium salt,sodium chloride, common in nature, that givesa salty flavor to ocean water and salt lakes.

SegmentationSuccessive cell divisions in the egg of an animalto form a multicellular blastula.

Sexual DimorphismAn assembly of external morphologicalcharacteristics that make it possible todistinguish the males from the females of thesame species.

Sexual ReproductionReproduction involving meiosis andfertilization.

Social InsectsInsects that live with others of the samespecies, looking after the young and gatheringfood for the community.

SpeciesA group of individuals that recognize oneanother as belonging to the samereproductive unit.

SpiracleOne of the external openings of the respiratorysystem in terrestrial arthropods.

StatocystA balance organ consisting of a sac-likestructure that contains grains of sand(statoliths) or some other material thatstimulates the sensory cells when the organismis in motion.

SubstrateThe surface that constitutes an organism'shabitat or life support.

SwarmInsects that act in a group for eating, mating,or finding a new location for a nest.

TagmosisThe process of segment formation(metameres) into corporal regions (tagmata)with differentiated functions.

TaxismAlso known as taxia, it is the orientation ofmovement in those organisms that, being ableto move freely from one place to another,track their course in the direction of anexternal stimulus.

TaxonomyStudy of the principles of scientificclassification. The organization, grouping, anddenomination of living things.

TentaclesLong and flexible organs located around themouth of many invertebrates, often prehensileand tactile.

ThoraxIn crustaceans and insects, the fused segmentslocated between the head and the abdomen towhich the legs are attached.

TissueGroup of similar cells organized in a structuraland functional unit.

TracheaIn insects and some other terrestrialarthropods, the system of air conduits coveredwith chitin.

VenomChemical agent injected into other animals inorder to kill or paralyze them, or to ward offan attack.

ZoologyDiscipline or science dedicated to the study ofanimals.

OrderTaxonomic category that includes families;category lower than a class and higher than a family.

OrganBody part made of various tissues grouped intoa structural and functional unit.

Organic MaterialAnimal or plant material in any stage ofdecomposition, found on or within the soil.

OrganismAny living creature, whether single-celled ormulticellular.

ParasiteOrganism that lives at the expense of another.

PhylumTaxonomic category that includes classes;category lower than a kingdom and higherthan a class.

PlanktonGroup of small living beings, whether plants(phytoplankton) or animals (zooplankton), thatlive suspended in freshwater or ocean water.

PlanulaType of unattached, ciliated larva of manyorganisms of the phylum Cnidaria (jellyfish, seaanemones, and coral).

PolypThe immobile stage in the life cycle of animalsof the phylum Cnidaria.

PopulationGroup of individuals of the same species thatlive in a certain area during a specific time.

96 INDEX INVERTEBRATES 97

Index

Aamber

air bubbles, 11ancient life–forms, 11color, 10fossils in, 10–11properties and characteristics, 11resin, 11

Amblypygi, 45American farmer ant, 75anemone, beadlet, 15annelid, 26Anomalocaris (fossil), 6, 7, 9ant

American farmer, 75anthill, 74–75aphids, 78–79black garden, 74, 79, 82blood–red, 13castes, 75communication, 74defense, 75diet, 75metamorphosis, 74mutualism, 78–79social organization, 74southern wood, 75species, 74trap–jaw, 75velvety tree, 75

Antarctic krill, 14antenna, 55, 74anthill, 74–75aphid, and ants, 78–79apiculture, 86–87aposematism (defense mechanism), 66, 76arachnid

color, 34dust mites, 84–85most dangerous, 50name source, 34species, 44, 45venomous, 50–51

arthropodsmall, 13success, 14

Asian tiger mosquito, 12auger beetle, 83Australia, Ediacara Hills fossils, 6, 8–9Australian centipede, 63Australian stick insect, 77Aysheaia (fossil), 9

Bbarnacle, 36beadlet anemone, 15bee

apiculture, 80–81dances, 13history of beekeeping, 80–81hive, artificial, 4, 80–81, 86–87honey collection and processing, 87mouth, 58nectar, 86organized communities, 5queen, 87vision, 56worker, 86, 87

beekeeping, 4, 5, 86–87beetle

antennae, 55aquatic, 68–69auger, 83burying, 13, 82click, 13common furniture, 13diving, 68flying, 66–67great diving, 17jaws, 55species, 13wings, 67

bigfin reef squid, 15bilateral symmetry, 54bivalve, 29

Canadia (fossil), 9caramote prawn, 14caterpillar, 70–71cedar beetle, antennae, 55centipede, 13, 55, 83

Australian, 63characteristics, 63Geophilomorpha, 63legs, 62life, 62megarian banded, 63walking, 62

cephalopod, 19, 29, 32Chagas disease, 82Chancelloria (fossil), 9Charnia (fossil), 8chelicerae, 44, 49

hunting spider, 50chitin, 38Christmas tree worm, 15chrysalis: See pupacicada, 67clam, 31click beetle, 13clown fish, 23Cnidaria

common characteristics, 22number of species, 21, 23types, 20–21

cockle shell, 29cockroach, 54, 70, 83cocoon: See pupacommon cuttlefish, 29common European oyster, 31common furniture beetle, 13common octopus, 15common pond skater, 16common starfish, 15copepod (Copepoda), 17, 37, 43coral, 22

cnidarians, 21reefs, 14, 22

cowry, tiger, 15crab

European green, 37

hermit, 39life cycle, 37movement, 40–41urchin, 15

crab spider, 49Cramer's blue morpho (butterfly), 12crayfish, white–clawed, 17cricket, mole, 54crustacean, 35

anatomy, 40body forms, 36–37environments, 34freshwater adaptations, 16marine, 14species, 14, 40

cuttlefishbroadclub, 14common, 29

Ddesert locust, 88desert millipede, 13desert scorpion, 51Dickinsonia (fossil), 8disease, and invertebrates, 82, 85diving beetle, 68diving bell spider, 17dog flea, 64–65dragonfly, 54, 70

emperor, 16, 70–73hawker, 54–55nymph, 17

drone, ants, 75Dublin Bay prawn, 40dust mite, 82

allergies, 85anatomy, 84–85humidity, 85size, 85

Dysdera crocota (spider), 49

Eearthworm, 13, 82

anatomy, 26echinoderm

classes, 20five–radial symmetry, 22history, 24number, 25species, 20, 22spiny skin, 20

Ediacara Hills fossils, 6, 8 elytron wing (elytra), 66, 67Emeraldella (fossil), 9emperor dragonfly, 16, 70emperor scorpion, 44European green crab, 37European hornet, 13European medicinal leech, 17, 91exoskeleton, moulting, 39eye

flatworms, 26insects, 56–57spiders, 49–50

Fflatworm, 26flea, 64, 83

bites, 65dog, 65food chain, 12human, 65jumping ability, 64life cycle, 65water, 43

flydiseases, 82metamorphosis, 72–73mouth, 60vision, 56–57wings, 67

pearls, 30black bean aphid, 79black garden ant (black ant), 74, 79black vine weevil, 13black widow spider, 50blood–fluke (bilharzia), 17blood–red ant, 13bloodletting (medicine), 90bloodsucking bug (triatomine), 82, 83body plan

bilateral symmetry, 54radial symmetry, 15, 20–21, 24

brachiopod, 43brimstone butterfly, 76–77brittle star, 20broadclub cuttlefish, 14Broussais, Francois J. V., 90brown garden snail, 13, 28–29Burgess Shale fossils, 6, 8, 9Burgessia (fossil), 9burying beetle, 13, 82butterfly

antennae, 55brimstone, 76–77Cramer's blue morpho, 12metamorphosis, 70–73monarch, 12, 70–73mouth, 58, 60owl, 76peacock, 76shape, 72–73

Ccaddisfly, larva, 17Cambrian Period

Burgess Shale, 8–9trilobite predator, 6–7trilobites, 9

camouflage (crypsis), 76–77octopus, 32pupa, 72

Canada, Burgess Shale fossils, 6

98 INDEX INVERTEBRATES 99

flying, insects, 66–67food chain

described, 42levels, 12

fossilamber, 10–11ancient life–forms, 10Burgess Shale, 6, 8–9Cambrian explosion, 8Ediacara Hills, 6evidence of ancient life, 10trilobites, 9

fruit fly, 72–73furniture beetle, common, 13

Ggarden, 82garden snail, brown, 13gastropod, 28Geophilomorpha centipede, 63giant household spider, 44giant squid, 15gills, 15grasshopper, 54great diving beetle, 17great pond snail, 17green mussel, 29

Hhair, 48, 49, 68hawker dragonfly, 54–55hermit crab, 39hive, artificial, 86–87home, human

black ants, 82burying beetles, 82dust mites, 85 earthworms, 82invertebrates, 82–83

ladybugs, 82pillbugs, 82snails, 82spiny–headed worm, 82

honeybees, 5collection and processing, 80, 86, 87

honeydew (aphid excretion), 79house dust mite, 82human flea, 65hunting spider, 50

Iinsect

anatomy, 54ants, 74–75aquatic beetles, 68antennae forms, 55, 58beetles, 67body symmetry, 54camouflage, 76–77carnivores, 58–59cicadas, 67common characteristics, 54diving, swimming, and skating, 68–69environments and life stages, 16evolutionary development, 5eyesight, 56–57flying, 66hardiness, 52–53human environment, 82–83jumping, 65known species, 54ladybugs, 66–67leaf eaters, 58living in trees, 12living near water, 16locusts, 59metamorphosis, 70–73mimetism, 76mouths, 55, 58plagues and illness, 82

food chain, 12identifying, 67seven–spotted, 58, 67species, 66

leechancient uses, 90body, 91European medicinal, 90–91medicinal, 17, 90mouth, 90movement, 91saliva, 91types, 90

life–form, first, 6lobster

American, 14anatomy, 41color, 38environment, 41exoskeleton, 38–39movement, 41pincers, 41shape change, 38

locust, 70antennae, 55best control, 89breeding zones, 89desert, 88history, 89mouth, 58–59plagues, 88–89rainfall, 89

luminescence, 42

MMalacostraca (crustacean), 36, 42mantis, thistle, 77Marrella splendens (fossil), 9mayfly, 16megarian banded centipede, 62–63metamorphosis, 70–73

ants, 74

changes, 70emperor dragonfly, 70fruit fly, 72–73hormones, 72monarch butterfly, 70–73simple, 70

millipede, 55anatomy, 62characteristics, 54desert, 13walking, 62

mimetism (defense mechanism), 76mite, 44

anatomy of dust, 84–85dust, 82sarcoptes, 84

mole cricket, 54mollusk

body, 28buried in sand, 29common characteristics, 28gastropods, 28types of, 28

molting (ecdysis), 39, 45, 72monarch butterfly, 12, 70–73mosquito

Asian tiger, 12diseases, 82face and mouth, 61female head and mouth, 61life cycle, 16mouth, 58

mussel, 29, 31mutualism, 78

Nnautilus (mollusk), 29nymph, 17, 70, 74

Ooctopus

characteristics, 29color, 32common, 15diet, 32environment, 14, 32head, 32ink, 33movement, 32speed, 33suckers, 33

ogrefaced spider, 49Olenoides (fossil), 9Opabinia (fossil), 9oriental cockroach, 83otter shell, 29Ottoia (fossil), 9owl butterfly, 76oxygen, gills, 15oyster, 15

anatomy, 31common European, 31pearls, 30–31

Ppalp (pedipalp), arachnids, 49parasite, 17, 44, 65parthenogenesis, 43peacock butterfly, 76pearl

cultivation, 30formation, 30oysters, 31producers, 31types, 30

pecten, scorpions, 51pedipalp (palp), arachnids, 49phytoplankton, 42pillbug, 13, 82

skating, 68sucking and piercing, 60–61water strider, 68wings, 54

invertebratebody plans, 15camouflage, 18freshwater, 16–17honey, 5human environment, 82–83known species, 4land, 12largest, 14marine, 14–15

JJapan, pearls, 30Japanese rhinoceros beetle, 55Japanese spider crab, 36jellyfish, 15, 18–19

cnidarian characteristics, 21Ediacaran fossils, 8habitat, 21life cycle, 21white, 15

jumping spider, 49

Kkrill (crustacean)

Antarctic, 14description, 42luminescence, 42

Lladybug (ladybird), 82

flying, 66–67

100 INDEX

plague of locusts, 88–89plankton, 37poison: See venompond skater, common, 16Porifera (sponge), 21prawn

anatomy, 40caramote, 14description, 37Dublin Bay, 40

praying mantis, 12Precambian period, Ediacara fauna, 8Prosobranchia (mollusk), 28pupa, 71, 72

Qqueen

ants, 75bees, 87

Rradial symmetry, 15, 20–21radiant sea urchin, 15razor clam, 29red starfish, 15reef, coral, 14, 22resilin (protein), fleas, 64

Ssalt, adaptation to freshwater environments, 17sarcoptes mite, 84scallop, 29scorpion

anatomy, 51description, 44desert, 51

emperor, 44families, 51habitat, 51hunting, 50

sea anemoneanatomy, 23cnidarian characteristics, 21dangerous, 23preferred environment, 23shape adaptation, 23

sea angel, 28sea cucumber, 15, 20sea lice, 36, 37sea lily, 20sea slug (Opisthobranchia), 15, 28sea urchin, 20

photoreceptors, 24radiant, 15varieties and characteristics, 25

seven–spotted ladybug, 58, 66shrimp, 40Sidneyia (fossil), 9silk, spiders, 45, 46–47silkworm, 13silverfish, 13slug

characteristics, 28sea, 15

snail, 82brown garden, 13, 28–29great pond, 17

southern wood ant, 75spider, 13, 83

anatomy, 45black widow, 50crab, 49diving bell, 17Dysdera crocota, 49food chain, 12fossilized in amber, 10–11giant household, 44hunting, 50jumping, 49ogrefaced, 49reproduction, 45

senses, 48–49sensory hairs, 48silk, 45, 46uses of silk thread, 47venom composition, 50web use, 5See also arachnid

spiderwebarchitecture, 47silk, 46use, 5

spinneret, 46spiny–headed worm, 82sponge, 15, 20squid

bigfin reef, 15characteristics, 29

starfishanatomy, 24–25common, 15movement, 25photoreceptors, 24red, 15suckers, 22

stick insect, Australian, 77stinger, scorpions, 51suction, 24, 33

Ttellin shell, 29telson (anatomy), 40, 42, 51termite, 83thistle mantis, 77tick, 13, 44, 84tiger cowry, 15toxin: See venomtrap–jaw ant, 75trichobothria hair, 48trichodina, 17trilobite (fossil), 9trophic chain, 42

Uurchin crab, 15uropod (anatomy), 40

Vvelvety tree ant, 75venom

ants, 75arachnids, 50–51centipedes, 62, 63octopus, 32sea anemones, 23scorpions, 44spiders, 45, 49

Wwandering spider, 50wasp, 13, 83

pollination, 5water beetle, 17water boatman (back swimmer), 16water flea, 43water measurer, 16water scorpion, 54water strider, 68, 69weevil, black vine, 13white–clawed crayfish, 17white jellyfish, 15Wiwaxia (fossil), 9wood louse, 36worker

ants, 75bees, 86, 87

worm, 82Christmas tree, 15classes, 26

digestive system, 26earthworm, 13known species, 27leeches, 90–91longest, 26reproduction, 27

XXandarella (fossil), 9

YYohaia (fossil), 9

Zzooplankton, 17

krill, 42Malacostraca, 42phytoplankton, 42species, 42–43

INVERTEBRATES 101