Social InsectsSocial Insects

Psychology 3107Psychology 3107

IntroductionIntroduction

Many Insects live in hives, nests or what Many Insects live in hives, nests or what have youhave you

Definite roles for different castes, usually Definite roles for different castes, usually only one female that lays eggsonly one female that lays eggs Other females are ‘sterile’Other females are ‘sterile’

An ExampleAn Example

The life history of the BumblebeeThe life history of the Bumblebee

Mated females emerge in spring after 8 Mated females emerge in spring after 8 months of hibernationmonths of hibernation Mated the previous autumnMated the previous autumn

Colony in which she was hatched is all Colony in which she was hatched is all deaddead

Up to 100 or so females left the colongyUp to 100 or so females left the colongy First she forages for pollenFirst she forages for pollen

The flight of the Bumblebee!The flight of the Bumblebee!

Pollen providesPollen provides Fat, minerals and vitamins for egg formationFat, minerals and vitamins for egg formation

Later on she forages for nectarLater on she forages for nectar Provides carbohydratesProvides carbohydrates

Stores nectar in wax containersStores nectar in wax containers

Lays eggs in the ‘Hall of Pollen’Lays eggs in the ‘Hall of Pollen’

First brood are sterile femalesFirst brood are sterile females forageforage

BzzzzzzzzzzzzzBzzzzzzzzzzzzz

Second brood are also sterile femalesSecond brood are also sterile females Cared for by the first broodCared for by the first brood

Third brood are fertile females and malesThird brood are fertile females and males Cared for by first and second broodCared for by first and second brood

Third brood leaves, males mate and die, Third brood leaves, males mate and die, females mate and hibernatefemales mate and hibernate

The colony is really just a reproductive The colony is really just a reproductive factoryfactory

EusocialityEusociality

For Eusociality we needFor Eusociality we need Overlapping generationsOverlapping generations Cooperative care of the youngCooperative care of the young Sterile castesSterile castes

In insects, euscociality occurs in:In insects, euscociality occurs in: HymenopteraHymenoptera

AntsAnts

BeesBees

waspswasps

EusocialityEusociality

IsopteraIsoptera TermitesTermites

HomopteraHomoptera AphidsAphids

Some say that these two are not truly Some say that these two are not truly eusocial, but if you look at that definition, eusocial, but if you look at that definition, you could, under certain circumstances, you could, under certain circumstances, say bees were not eusocial!say bees were not eusocial!

HaplodiploidyHaplodiploidy

Eusociality has evolved 11 separate times Eusociality has evolved 11 separate times just in Hymenoptera!just in Hymenoptera!

Why?Why? Sterile females are usually very closely Sterile females are usually very closely

relatedrelated Basically, it does not pay to have young, it Basically, it does not pay to have young, it

pays more to take care of your sisters, as they pays more to take care of your sisters, as they are more closely related to you than any are more closely related to you than any potential offspring!potential offspring!

Haplowhatoidy?Haplowhatoidy?

DaughterDaughter SonSon MotherMother FatherFather

.5.5 .5.5 .5.5 .5.5 femalefemale

1.01.0 00 11 00 malemale

SisterSister BrotherBrother.75.75 .25.25 femalefemale.50.50 .50.50 malemale

So you see, sisters are either 75 % related, or 100% related or 50% related, averages out to 75 %

Males are just clones of half of female chromosomes

So, what’s the deal with…..So, what’s the deal with…..

TermitesTermites

They aren’t They aren’t haplodiploidhaplodiploid

They are eusocialThey are eusocial

There is a king tooThere is a king too

Queen is an egg Queen is an egg laying machinelaying machine

While you’re at it, explainWhile you’re at it, explain

Naked mole ratsNaked mole rats MammalsMammals

‘‘Penises with teeth’Penises with teeth’

Both with the termites Both with the termites and the NMR we and the NMR we have cases of have cases of eusociality, but also eusociality, but also normal diploid normal diploid reproductionreproduction

ConclusionConclusion

Social insects are a great example of the Social insects are a great example of the predictions of genetics and evolution at predictions of genetics and evolution at work.work.

Termites and naked mole rats show that Termites and naked mole rats show that eusociality is not simply due to eusociality is not simply due to haplodiploidyhaplodiploidy Gene environment interaction baby!Gene environment interaction baby!