Why learn about insects? - Rivanna Master Naturalists · Why learn about insects? "the insects are so numerous that if they were divided equally among each one of the earth's 6 billion

Why learn about insects?

Rivanna Master Naturalists

21 April 2015

Linda S. Fink

Duberg Professor of Ecology

Sweet Briar College

Goals for Insect Week

Understand

1. features that characterize arthropods in general, insects specifically

2. how much variation there is in all aspects of insect biology

3. ecological, economic, public health importance of insects

Feel prepared to

4. participate in insect projects as Master Naturalists

children's and school programs

pollinator and foodplant gardening

monitor native insect populations, stream health, exotic insects

measure biodiversity (e.g. bioblitz, NABA butterfly count)

citizen science (e.g. Journey North, Monarch Watch)

5. learn more about insects

Numbers of

described

species

(approximate)


Dominant multicellular life form on the planet

• Number of species

• Numbers of individuals

• Biomass

A “species scape”


"the insects are so numerous that if they were

divided equally among each one of the earth's 6

billion human inhabitants, each of us would be

allotted 1 x 1018 insects -- that's a billion billion --

1,000,000,000,000,000,000." [J. Myers, several

years ago!]

locusts

mayflies

monarch

butterflies


Ecological rolespollination

seed dispersal

fungal dispersal

nutrient cycling

predators and parasites

prey

phytophagy


Ecological rolespollination

seed dispersal

fungal dispersal

nutrient cycling

predators and parasites

prey

phytophagyphyto- plant

phag(o)- eat

stem borer

fruit pest

leaf miner phloem feeder


Human requirementsAgriculture and food production

beneficial and harmful

Health and disease

human, livestock, companion animals, plants

Scientific discovery

Culture

Economics


Health and disease (human, livestock, companion animals): Medical and Veterinary Entomology

mosquito life cycle

Mosquito-borne diseases

Encephalitis

West Nile Virus

Equine encephalitis

Malaria (Plasmodium, protist)

Yellow fever (virus)

Dengue fever

West Nile Virus incidence, US, 2008

Other insect-borne diseases

Typhus: Rickettsia bacteria, R. prowazekii

Vector = body louse, Pediculus humanus corporis

multiple epidemics of historic significance include:

Irish famine (1846-1849)

WWI (millions of deaths)

WWII (Nazi concentration camps)

Plague: bacteria, Yersinia pestis

Vector = flea

Reservoirs = rodents, including rats

Justinian plague (6th c): killed > 100 million

"Black Death" (14th c): killed 60% of European pop

Trypanosoma (protists)

African trypanosomiasis / sleeping sickness (tsetse fly vector)

10,000 new cases / year (WHO)

American trypanosomiasis / Chagas disease (reduviid bug vector) affects 8-11 million people in the Neotropics (CDC)

flea

body louse

Triatoma infestans

Why learn about insects ticks?

Diseases transmitted by ticksLyme disease

Rocky Mountain Spotted Fever

Ehrlichiosis

Babesiosis

Rickettsiosis

Economic value, negative

Insects consume or destroy

•10% of GNP in large, industrialized nations

•up to 25% of GNP in some developing countries

Malaria control, elimination, and research & development

• $ 5-6 billion per year

Economic value, positive

Increased crop value from bee pollination

• more than $15 billion per year

Beneficial predators and parasites reduce

crop losses from agricultural pests

• $4.5 billion per year

“If all mankind were to disappear, the

world would regenerate back to the

rich state of equilibrium that existed

ten thousand years ago. If insects were

to vanish, the environment would

collapse into chaos.”

E. O. Wilson

But the best reason to study insects is...


they are amazing


they are amazing

Alex Wild


they are amazing

Alex Wild


they are amazing

Alex Wild


they are amazing

http://planetapex.blogspot.com

Who are the insects?

Who are their relatives?

Traditional Classification

Kingdom

Phylum

Class

Order

Family

Genus

Species


Kingdom: Animal

Phylum: Major body plans

sponges chordates segmented worms

roundwormsmolluscs echinoderms

Phylum: Arthropods

spiders

scorpions

crustaceans

centipedes

horseshoe crab

insects

and more...

Let's look at some animals....

Arthropod Characteristics

• External hardened skeleton of cuticle

• Periodically shed exoskeleton to grow (molt, ecdysis)*

• Segmented body is organized into 2 or 3 functional units

• Jointed, paired appendages

• More than two pairs of limbs

• * trait shared with several other phyla

Let’s look at the external skeleton

Functions

Physical protection

Waterproofing

Sites for muscle attachment

Locations for sensory receptors

all photos from Alex Wild

Variation in exoskeletons

Honeypot ants (Camponotus inflatus)

membrane

dorsal sclerite

Alex Wild

Variation in exoskeletons

Coloration

pigment molecules in the cuticle

Coloration

structural colorsphysical characteristics affect light

scattering

interference

diffraction of light

Sensory structures: Chemoreceptors

Sensory structures: Mechanoreceptors

Sensory structures: Visual receptors

PROBLEMS WITH HAVING AN

EXOSKELETON?

nutmeg66 on flickr.com

britannica.com

pinebaskets.tripod.com

•External skeleton is not cellular

•it doesn’t grow

•To increase in size, an arthropod must

•shed its old skeleton

•produce a larger one

•Molting (ecdysis)

nutmeg66 on flickr.com

britannica.com

pinebaskets.tripod.com

Molting (ecdysis) is risky

physical injury

dessication

predation

Molting is associated with both

growth and development

Molting is associated with both

growth and development


Kingdom

Phylum

Class

Order

Family

Genus

Species

What are the major groups of Arthropods?

Kingdom: Animal

Phylum: Arthropod

Class

Distinguishing characteristics: body regions

crustaceantrilobite

chelicerate

myriapod

hexapod

Distinguishing characteristics: appendages

crustaceantrilobite

chelicerate

myriapod: 1 pair antennae, many limbs

hexapod: 3 pair of legs

& 0-2 pair of wings on

thorax; 1 pair of

antennae

Crustaceans

• two body regions: cephalothorax and abdomen

• two pairs of antennae

• most appendages are two-branched

Chelicerates

• two body regions: cephalothorax and abdomen

• lack antennae

• six pairs of unbranched appendages

• 1st appendage pair = chelicerae (jaws)

• 2nd appendage pair = pedipalps. These may appear leglike or may be highly modified

• pairs 3-6 = leglike

jumping spider

chelicera

pedipalp

pedipalp

pseudoscorpion

Chelicerates

•Arachnids (spiders, mites,

ticks, scorpions)

Myriapods

• Two body regions:

head and trunk

•One pair of antennae

• Appendages

unbranched

• Many pairs of legs

•Millipedes: most are

herbivores or detritivores

•Centipedes: most are

carnivores

Hexapods

• Three body regions: head, thorax, abdomen

• one pair antennae

• three pairs of legs on the thorax

protura

dipluraspringtails

(Collembola)

photo by Alex Wild

Collembola

Collembola

Podura aquatica lives on surface of ponds!

Hexapods




protura

dipluraspringtails

(Collembola)

photo by Alex Wild

and, of course, the

hexapods include the

INSECTS

Insects




photo by Alex Wild

Quick Review

What features

distinguish

ARTHROPODS from

other animal phyla?

What features

distinguish INSECTS

from other arthropod

classes?

ANIMALS

ARTHROPODS

INSECTS

multicellular

heterotrophicexternal skeleton

molt

jointed appendages

3 body regions

1 pair antennae

3 pair of legs

Let’s take a break

Documents

Why learn about insects? - Rivanna Master Naturalists · Why learn about insects? "the insects are so numerous that if they were divided equally among each one of the earth's 6 billion