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Insect Societies

Insect Societies. Lecture 21. Insect sociality. Co-operative behaviors Eusocial: co-operate in reproduction and have division of reproductive effort (bees, wasps, ants, termites) Subsocial : less developed social habits (many insects) Solitary: no social behaviors (most insects).

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Insect Societies

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  1. Insect Societies Lecture 21

  2. Insect sociality • Co-operative behaviors • Eusocial: co-operate in reproduction and have division of reproductive effort (bees, wasps, ants, termites) • Subsocial: less developed social habits (many insects) • Solitary: no social behaviors (most insects)

  3. Subsociality in insects • Aggregation • Often aposematic

  4. Subsociality in insects • Parental care • Without nesting (Belostomatidae example) • With solitary nesting (Silphidae example) • With communal nesting (Sphecidae example) • Nesting: eggs are laid in a pre-existing or newly constructed structure to which the parents being food supplies for the young

  5. Parental care without nesting • Giant water bugs (Belostomatidae) exhibit paternal egg-tending

  6. Parental care with solitary nesting • Carrion beetles (Silphidae: Nicrophorus) display extended biparental care of young and reproductive cooperation between the sexes

  7. Parental care with communal nesting • Digger wasps (Sphecidae) share nest with others and females remain in the nest and guard

  8. Subsociality in insects • Sterile soldier caste • Subsocial aphids (Pseudoregmasp.)

  9. Eusociality in insects • Division of labor, with a caste system involving sterile or non-reproductive individuals assisting reproductive individuals • Co-operation among colony members in tending the young • Overlap of generations capable of contributing to colony functioning Eusociality is only known from Hymenoptera (bees, wasps, ants) and Termitoidae (Blattodea)

  10. Eusociality in Hymenoptera • Queen, drones, worker, soldiers • Haplodiploid genetic system in which queens control the sex of their offspring • Males develop from unfertilized eggs, thus haploid • Females develop from fertilized eggs, thus diploid • Behavioral and chemical maintenance of monarchy • Division of labor by polyphenism or polyethism

  11. Haplodiploidy: a precursor to eusociality?

  12. SOL: Solitary SUB: Subsocial EU: Eusocial

  13. Wasp (Vespulasp.) • Female caste dimorphic (queen and worker) • Age polyethism • Newly emerged workers involve in nest construction and food distribution • Middle-aged workers involve in foraging • Old-aged workers involved in guarding

  14. Wasp Nest building

  15. Honey bee (Apismellifera) • Female dimorphism: queen and worker • Workers have wax glands and pollen-collecting apparatus (corbicula and combs), barbed stinger • Workers exhibit polyethism • Caste differentiation trophogenic (determined by food)

  16. Honey bee (Apismellifera)

  17. Ants (Formicidae) • Two major female castes: reproductive queen and workers • Some species have polymorphic workers: minor, media, major workers • Caste determination trophogenic

  18. Termites (Termitoidae) • Primary reproductives: queen and king • Supplementary reproductives: potentially reproductive, but with arrested development • Sterile termites: workers and soldiers (nasus) • Nymphs: developmental instars of reproductives • Larvae: instars of sterile lineages

  19. Role of JH in caste differentiation Physogastry: termite queen’s abdomen being distended to 500-1000% of its original size

  20. Evolution of eusociality • Kin selection: evolutionary strategy that favors the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction • rB > C where r = coefficient of relatedness, B = benefit gained by the recipient of altruism, C = cost suffered by the donor of altruism • Subsociality might be a precursor to eusociality

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