sign in sign up
<<
Home , Halictinae, Sociality

4/22/18

Social

• evolved multiple times in insects Social Insects • Much of Earth’s fauna consists of social insects • They play major roles in Ecology entire ecosystems • Proliferation of and associated with change from solitary to social lifestyle

Social Insects Subsocial

• Consistent trend: • More widespread • Numerous forms of subsocial – 13 orders of insects in numerous lineages – Aggregations TO – no reproductive – Parental care TO division of labor – Parental care & nesting TO – Communal nesting TO • Increasing division of labor and in fewer lineages TO • Primitively eusocial in fewer lineages TO • Advanced eusocial fewer lineages

1 4/22/18

Eusocial Aggregations as subsocial behavior

• Three traits • Food exploitation – Some individuals in – bark reproduce, others sacrifice reproduction • Roosting – Cooperation in tending young – Overlap of generations within colonies • Ants, termites, some and

Aggregations as subsocial behavior Parental care

• What parental care do • all insects provide? • Post hatching attention, – monarch butterflies provision and protection – ladybird beetles of food • Chemical defenses – Without nesting – • Tending and • Parental care young – Care of – Can involve feeding – , , Dermaptera, , Coleoptera and

2 4/22/18

Membracid nannies Nesting as

• Parental care by ants. • Eggs laid in • Ants obtain structure and honeydew from parents tend young – Types of • New construction • Pre-existing – Types of care • Vigilence • Nutrition

Nesting as social behavior Nesting as social behavior

• Solitary nesting – No reproductive division of labor – Examples: • ground nesting crickets, • , angel insects • some beetles, Most nesting • Hymenoptera subsocial – What orders? Hymenoptera are – Nesting is not known in parasitoid wasps. other orders.

3 4/22/18

Communal nesting Social aphids &

• Nests shared among individuals • Aphids • Parents clean, – Behavioral and provision, defend morphological differences nests 1. Soldiers • Conflicts among • All first instar • molt into normal nest mates common feeding individuals • Halictinae, • Reproduction delayed Megachilinae, if molt is delayed 2. Special caste of Andreninae soldiers

Social aphids

Soldier nymphs Social aphids Remain at 2nd instar without molting and growing. Sclerotized cuticle Sterile Adults Attack natural enemies & competitors Perform housekeeping. Differences likely Genetically identical clones by attributable to parthenogenesis differences in expression between the castes POLYPHENISM Molt and grow. Soft cuticle. Contribute to reproduction. Perform neither defense nor house- Soldiers injecting venom into predatory keeping. lacewing Reproductive (normal) nymphs

4 4/22/18

Social aphids & thrips Social thrips

• Thrips – Behavioral and morphological differences – Dispersers & soldiers in colony in gall – Soldiers defend gall against other thrips Dispersers are Soldiers have low highly fecund, fecundity and are and usually involved primarily in reproduce less than participate in extensive brood defense of the gall from kleptoparasites. dispersers care, and are adept at initiating and They cannot initiate or growing new galls. grow galls.

Quasisociality & Semisociality

• Communal nest- adults cohabit a single • Multigenerational colonies nest, but each care for their own young. • Polyphenism: morphological differences • Quasisociality- adults cohabit a single nest, between queen and workers and cooperate in brood care. • Polyethism: behavioral • Semisociality differences • Caste system – Division of reproductive labor – Reproductives – Workers are sisters to queens – Workers • =caste system – Soldiers • No morphological difference between queen and workers – Subcastes – No overlap of adult generations • Found only in Hymenoptera and ALL Isoptera

5 4/22/18

Natural selection & Eusociality & Eusociality

• Why would some • W.D. Hamilton gave us individuals NOT be the tools to solve one of involved in Darwin’s greatest reproduction? challenges. • The of altruism.

Eusocial Hymenoptera Super-relatedness in Hymenoptera

• What sex-determination system do all • Why are there so Hymenoptera have? many origins of • So, what is the genetic Eusociality in the relatedness between Hymenoptera? sisters? • How could this result in • How are ‘r’ and ‘B’ a maximization of ‘r’? maximized with • What benefits might respect to ‘C’? there be of this extensive social behavior?

6 4/22/18

Eusocial Hymenoptera Hymenoptera

• Numerous origins of eusociality from subsociality. • Primitively eusocial – Females morphologically similar – Colonies usually annual • Advanced eusocial • Which is/are the male(s) in the above figure? – Ants, some wasps, many bees • Which is/are the female(s) in the above figure? – Behavioral and morphological • Feeding quality + substance yields polyphenism differentiation in diploids, which are all ______. – Workers different than queens

Primitive eusocial Hymenoptera Bumblebees

• Numerous transitional lineages, e.g.: • Polistine Wasps, a few others – >1 female forms colony – Colony lasts 1 yr – Variable # reproductives • Bumblebees, Halictinae – >1 female forms colony – ‘winning’ female • Colony foundation by one or more females reproduces and is • Pheromones used to modify worker behavior aggressive – Sexual retardation • Ovarian development in late season workers reversed if queen dies • Queen may be driven from nest • Workers produce male offspring parthenogenetically

7 4/22/18

Advanced eusocial Hymenoptera Eusocial honeybees ()

• Many bees and some wasps, ants • Females dimorphic • Specialization of workers • Wasps – Queen founds first • Colony develops and may found new colonies during brood of workers summer – Subsequent • Nest made of wax secreted by bees generations include males, then • Castes: queen (larger), worker (smaller), drone reproductive females • Old workers: hive; Young workers: field

Extreme eusociality: ants (Formicidae) Extreme eusociality: ants (Formicidae)

• All ants are eusocial • All ants are eusocial • Workers may be • Workers may be Amblyopone polyphenic are specialist polyphenic predators of – Trophogenic centipedes – Trophogenic – Feeding – Feeding • Predatory • Mutualists with plants • Seed and grain • Honey dew specialists harvesters

8 4/22/18

Extreme eusociality: ants (Formicidae)

• All ants are eusocial • Workers may be polyphenic – Trophogenic – Feeding • Fungus harvesters

Extreme eusociality: ants (Formicidae)

• All ants are eusocial • Workers may be Polyerges polyphenic Slave-maker – Trophogenic – Feeding • Parasites (slave-makers & usurpers) Formica Slave

A queen Polyergus slave-raiding attended to by a Formica worker. Parasitic queens such as Polyergus emit pheromones that are attractive to host ant workers

9 4/22/18

Extreme eusociality: ants (Formicidae) Eusocial Isoptera

• All ants are eusocial • What sex determination • Workers may be Polyerges polyphenic Slave-maker system do termites have? – Trophogenic – Feeding • Uh-oh, ‘zup? • Predatory • Perhaps something Formica about maximizing ‘B’ • Seed and grain Slave harvesters when feeding on wood? • Mutualists with plants • What else happens to wood-feeding insects in • Honey dew specialists their population • Fungus harvesters structure (remember the • Parasites (slave-makers Normark paper)? & usurpers) A queen Polyergus slave-raiding ant attended to by a Formica worker. Parasitic queens such as Polyergus emit pheromones that are attractive to host ant workers

Eusocial Isoptera Termites

• In what way does • Lower termites this caste – Wood-digesting determination endosymbionts – Loose castes, all structure differ from workers immature Hymenoptera? – Morphology and caste may change after molting – Queen similar to workers

10 4/22/18

Termites mounds

• Higher termites: Termitidae – No symbiotic flagellates • How do they digest wood? – Rigid caste system – Queen differs from workers: Physogastry

11