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Insect Societies Lecture 21. Insect sociality Co-operative behaviors – Eusocial: co-operate in reproduction and have division of reproductive effort (bees,

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Presentation on theme: "Insect Societies Lecture 21. Insect sociality Co-operative behaviors – Eusocial: co-operate in reproduction and have division of reproductive effort (bees,"— Presentation transcript:

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 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 Subsociality in insects

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 (Pseudoregma sp.)

9 Eusociality in insects 1.Division of labor, with a caste system involving sterile or non-reproductive individuals assisting reproductive individuals 2.Co-operation among colony members in tending the young 3.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 (Vespula sp.) 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 (Apis mellifera) 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 (Apis mellifera)

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 Physogastry: termite queens abdomen being distended to % of its original size Role of JH in caste differentiation

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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