entomology exam 3: insect societies/social behavior

four levels of social behavior

-solitary

-aggregation: grouping together for reproduction or other reasons

-subsocial: communal, some care for young

-eusocial("true" social): cooperative brood care, overlapping generations, divisions of labor (caste system)

ant/termite social behaviors

-antennation

-jittering

-trail laying/following (ex: termites follow trail drawn by bic pen)

-biting/grappling/stinging

-used to communicate, distinguish kin from foe (predators/pathogens)

trophallaxis

-transfer of food or other fluids among members of a community

-mouth-to-mouth (stomodeal)

-anus-to-mouth (proctodeal)

-common in termites and ants

allogrooming

-practice of grooming other members of the same social groups

-termites and ants

corpse removal/burial/cannibalism

-removing, burying, or eating infected corpses from colony to protect population

chemoreception

-used to detect semiochemicals

-taste (gustation): solid/aqueous chemicals, used to detect chemicals that adhere to substrate or outside of insect body

-smell (olfaction): airborne chemicals, used for remote chemoreception

-chemoreceptors common on feet, antennae, palps, and ovipositors

-ex: Bombyx mori (silk moth) antennae have sensory hairs that detect female sex pheromones

taste (gustatory) receptors

-thickwalled hairs, pegs, or pits where dendrites of several sensory neurons are exposed to environment through pore in cuticle

-each neuron responds to different range of compounds (ex: sugar, salt, water, protein, acid, etc.)

-found most on mouthparts

-also on antennae, tarsi and genitalia (especially ovipositor)

smell (olfactory) receptors

-thinwalled pegs, cones, or plates w/ numerous pores where airborne molecules diffuse

-dendrites branch within pores and respond to low concentrations of compounds (ex: sex pheromones)

-general or highly specific receptors

-abundant on antennae

-mouthparts or external genitalia

semiochemicals

-pheromones

-allelochemicals

pheromones

-chemical signals that carry info from one individual to another member of same species

-sex attractants

-trail marking compounds

-alarm substances

allelochemicals

-signals that travel from one individual to a member of different species

-defensive signals

-repellants

-compounds used to locate suitable plant hosts

three divisions of allelochemicals

-based on who benefits from message

1. allomones: benefit sender (repellant or defensive compound, like cyanide, that deters predators)

2. kairomones: benefit receiver (ex: odor a parasite uses to find its host)

3. synomones: benefit both (plant volatiles that attract insect pollinators)

altruism & eusociality

-ex: female larvae develop as workers instead of queens

-idea of doing selfless things to benefit a social colony even though it doesn't benefit individual

-ex: weaver ants

group selection theory

-groups w/ self-sacrificing (altruistic) individuals are more likely to survive than those without

inclusive fitness

-natural (direct) selection: selection on individuals differing in their # of surviving offspring

-kin (indirect) selection theory: selection on individuals differing in the # of non-descendent offspring they help to survive

-used to determine relative genetic success or interpret behaviors & behavioral strategies

indirect fitness dependence

-most eusocial societies depend entirely on indirect fitness

-reproductive division of labor

-cooperative care of offspring

-overlapping generations in same home

-reproduction in eusocial societies depend on sterile offspring to help them rear more offspring

-enormously productive; compensates for loss of direct fitness

inclusive fitness

-direct fitness + indirect fitness

-sterile colony members care for offspring with whom they share genes

-some of these kin may become future leader of their reproductive empire

hamilton's rule & altruism

rB>C

-r=relatedness (proportion of shares genes)

-B=benefit of recipient (how many more offspring are produced)

-C=cost to the altruist

-coefficient of relatedness: probability that an allele in one individual is present in another b/c both have inherited it from a recent common ancestor

eusocial animal groups

-termites (2,800 species)

-thrips (<25 spp. eusocial)

-aphids (50 spp.)

-ambrosia beetles (1 spp. eusocial)

-hymenoptera (18,000 species)

haplodiploidy

-females diploid, males haploid

-relatedness asymmetries among family members

-full of sisters

-requirement for eusociality: precious resource & limited ability to disperse

female workers

-ants, wasps, bees: relatedness asymmetries persist, sister helpers

-termites: no relatedness asymmetry, diploid, male and female helpers

-aphids&thrips: haplodiploid, high relatedness through inbreeding or cloning, both sexes help

male-female conflict in Polistes dominulus

-worker daughters of the dominant female have an interest in promoting survival of sisters (who may be future reproductive) over their brothers

-when food is brought back to the nest, workers start pushing males head first into cell ("male stuffing")

-aggressive behavior: biting and sting threat, pushes him into cell, continues head butting abdomen

-"stuffed" males stay in cells 6x longer than workers

queen-worker conflict over sex allocation

-queens prefer 1:1 F:M sex ratio (primary control: can control sex of eggs they lay

-workers prefer 3:1 F:M sex ratio (secondary control: can control which eggs they care for)

-polyandrous queens: workers no longer interested in only sisters and sex ratio gets closer to 1:1.

eusocial hymenoptera

-apidae: fully eusocial

-halictidae: partly eusocial

-formicidae: fully eusocial

-vespinae: fully eusocial

-polistinae: fully eusocial

-stenogastrinae: subsocial and eusocial