SOCIALITY IN INSECTS

Social Insects - Importance One colony - 306,000,000 workers - 1,000,000 queens - 45,000 interconnected nests - 2.7 km2 Formica yessensis

Social Insects - Importance Pollinators

Sociality Eusociality 1. Division of labour with caste system 2. Cooperation in tending young 3. Overlap of generations Subsociality

Subsocial Groups 1. Aggregations - non reproductive Pentatomid bugs

Subsocial Groups 1. Aggregations - non reproductive Monarch (Danaus) butterflies

Subsociality - parental care Oviposition preferences - Corixidae % on each substrate Wood Plexiglas Elodea - Aiken ‘81

Subsociality - parental care Male Abedus

Subsociality - parental care a) Without nesting - remove tending parent Predation Parasitism Diseases

Subsociality - parental care a) Without nesting Membracidae (treehoppers - Homoptera) Bugs - secrete honeydew Attracts ants Ants deter predators Female bugs leave early

SO FAR: Subsociality Aggregations Parental care Without nesting With nesting Solitary nesting Communal nesting

Parental Care - With Nesting Nest - parents use or make some structure - lay eggs - provision young Found in - Orthoptera - Dermaptera - Coleoptera - Hymenoptera Dermaptera (earwigs)

Solitary Nesting in the Hymenoptera - immoblize arthropod prey and provision young 1. Provision prey in its own burrow 2. Dig burrow after prey capture 3. Dig burrow before prey capture 4. Build a solitary structure 5. Build structures in aggregations

Subsociality in other Orders Homoptera - aphids Normal nymph “Soldier” nymph

Subsociality in other Orders Thysanoptera - thrips Normal female Soldier nymph

Quasi- and Semisociality - subsocial - all females reproduce Quasisocial - communal nest - members of same generation - all assist in brood rearing - all females can lay eggs Semisocial - communal nest - members of same generation - all assist in brood rearing - only 1 female can lay eggs - females are sisters (not daughters of queen)

Quasi- and Semisociality In Social Hymenoptera -division of labour -variability in fecundity Fully reproductive Reduced fecundity in groups halictine bees Quasisocial Some lay only male eggs (workers of Bombus) Worker sterility Super reproductive queen Semisocial

Sociality among groups of Hymenoptera solitary subsocial eusocial Apinae Megachilinae Adreninae Colletinae Halictinae Crabronidae Sphecidae Other vespoids Formicidae Scoliiidae Eumeninae Stenogastrinae Polistinae Vespinae Chrysidoidea Rest of Apocrita

Eusocial Hymenoptera

Eusocial Hymenoptera Fertilized 2N Egg (Female[worker]) Unfertilized N Egg (Male[drone])

Eusocial Hymenoptera Wasps Founding queen -builds nest -produces and feeds first brood Stops foraging -becomes purely reproductive Later in season - produce more males and new queens

Eusocial Hymenoptera Wasps Jobs of workers YOUNG -distribution of protein-rich food to larvae MIDDLE AGE -distribution of carbohydrate-rich food to adults OLD -clean cells and dispose of dead larvae -ventilation and air-conditioning of nest -construction and repair of nest -foraging - wood pulp, fluids, prey -nest defence

Caste Differentiation in Bees

Caste Differentiation in Bees Royal Jelly

Caste Differentiation in Bees Royal Jelly Hypopharyngeal glands

Caste Differentiation in Bees Royal Jelly

Caste Differentiation in Bees Royal Jelly Protein Carbohydrate Lipid N D J F A M J J A

Eusociality in Termites Reproductive castes Primary reproductives - King + Queen Supplementary reproductives - Neotenics Non-reproductive castes Workers Soldiers

Assumption: Subsociality is a necessary precursor for (and primitive to) eusociality Cryptocercus - a wood roach - Blattodea √ - symbionts in hind gut √ colonies - mated pair + 15  25 offspring - transfer symbionts by eating exuviae √ - nymphs help in nest maintenance Conclusion: These animals represent an evolutionary precursor to Isoptera (termites)

Assumption: Subsociality is a necessary precursor for (and primitive to) eusociality BLATTODEA Polyphagidae (including Cryptocercus) ISOPTERA Other families MANTODEA

Termitidae - Pathways for Caste Development Large worker 5 Alate Nymph 5 Large worker 4 Nymph 4 Small soldier Large soldier Large worker 3 Nymph 3 Small presoldier Small worker 2 Large presoldier Large worker 2 Nymph 2 Small worker 1 Large worker 1 Nymph 1 Small larvae (2nd) Large larvae (2nd) Larva (1st) egg King + Queen

Caste Development in Lower Termites Hormonal Control of Castes 1. Remove King and Queen 2. Divide colony with membrane 1. Re-introduce King and Queen - into membrane No change Pseudergates develop into reproductives

Why should a female bee (adult) sacrifice her own reproduction for that of the colony ?

Kin Selection and Inclusive Fitness Fitness comes from Your own reproduction Reproduction of relatives Inclusive Fitness

  In Social Hymenoptera Males are haploid - N Sperm contain 100% of paternal genes Females are diploid - 2N Eggs contain 50% of maternal genes  Offspring (daughters/workers) -have all of father’s genes Full sisters share 3/4 of their genes -have 1/2 of mother’s genes  Workers are more related to each other than their mother