Social Insects Psychology 3107

Introduction Many Insects live in hives, nests or what have you Definite roles for different castes, usually only one female that lays eggs Other females are ‘sterile’ Other females are ‘sterile’

An Example The life history of the Bumblebee Mated females emerge in spring after 8 months of hibernation Mated the previous autumn Mated the previous autumn Colony in which she was hatched is all dead Up to 100 or so females left the colongy First she forages for pollen First she forages for pollen

The flight of the Bumblebee! Pollen provides Fat, minerals and vitamins for egg formation Fat, minerals and vitamins for egg formation Later on she forages for nectar Provides carbohydrates Provides carbohydrates Stores nectar in wax containers Lays eggs in the ‘Hall of Pollen’ First brood are sterile females forage forage

Bzzzzzzzzzzzzz Second brood are also sterile females Cared for by the first brood Cared for by the first brood Third brood are fertile females and males Cared for by first and second brood Cared for by first and second brood Third brood leaves, males mate and die, females mate and hibernate The colony is really just a reproductive factory

Eusociality For Eusociality we need Overlapping generations Overlapping generations Cooperative care of the young Cooperative care of the young Sterile castes Sterile castes In insects, euscociality occurs in: Hymenoptera HymenopteraAntsBeeswasps

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

Haplodiploidy Eusociality has evolved 11 separate times just in Hymenoptera! Why? Sterile females are usually very closely related Sterile females are usually very closely related Basically, it does not pay to have young, it pays more to take care of your sisters, as they are more closely related to you than any potential offspring! Basically, it does not pay to have young, it pays more to take care of your sisters, as they are more closely related to you than any potential offspring!

Haplowhatoidy? DaughterSonMotherFather female male SisterBrother.75.25female.50.50male

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….. Termites They aren’t haplodiploid They are eusocial There is a king too Queen is an egg laying machine

While you’re at it, explain Naked mole rats Mammals Mammals ‘Penises with teeth’ Both with the termites and the NMR we have cases of eusociality, but also normal diploid reproduction

Conclusion Social insects are a great example of the predictions of genetics and evolution at work. Termites and naked mole rats show that eusociality is not simply due to haplodiploidy Gene environment interaction baby! Gene environment interaction baby!