Social Insects

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Social Insects

• Psychology 3107

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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

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An Example

• The life history of the Bumblebee
• Mated females emerge in spring after 8 months of
  hibernation
• 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

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The flight of the Bumblebee!

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

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Bzzzzzzzzzzzzz

• Second brood are also sterile females
• Cared for by the first brood
• Third brood are fertile females and males
• 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

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Eusociality

• For Eusociality we need
• Overlapping generations
• Cooperative care of the young
• Sterile castes
• In insects, euscociality occurs in
• Hymenoptera
• Ants
• Bees
• wasps

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Eusociality

• Isoptera
• Termites
• Homoptera
• 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!

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Haplodiploidy

• Eusociality has evolved 11 separate times just in
  Hymenoptera!
• Why?
• 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!

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Haplowhatoidy?

• Daughter Son Mother Father
• .5 .5 .5 .5 female
• 1.0 0 1 0 male
• Sister Brother
• .75 .25 female
• .50 .50 male

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Males are just clones of half of female
chromosomes
So you see, sisters are either 75 related, or
100 related or 50 related, averages out to 75
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So, whats the deal with..

• Termites
• They arent haplodiploid
• They are eusocial
• There is a king too
• Queen is an egg laying machine

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While youre at it, explain

• Naked mole rats
• Mammals
• Penises with teeth
• Both with the termites and the NMR we have cases
  of eusociality, but also normal diploid
  reproduction

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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!