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SOCIALITY IN INSECTS
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Social Insects - Importance
One colony - 306,000,000 workers - 1,000,000 queens - 45,000 interconnected nests - 2.7 km2 Formica yessensis
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Social Insects - Importance
Pollinators
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Sociality Eusociality 1. Division of labour with caste system 2. Cooperation in tending young 3. Overlap of generations Subsociality
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Subsocial Groups 1. Aggregations - non reproductive Pentatomid bugs
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Subsocial Groups 1. Aggregations - non reproductive Monarch (Danaus) butterflies
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Subsociality - parental care
Oviposition preferences - Corixidae % on each substrate Wood Plexiglas Elodea - Aiken ‘81
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Subsociality - parental care
Male Abedus
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Subsociality - parental care
a) Without nesting - remove tending parent Predation Parasitism Diseases
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Subsociality - parental care
a) Without nesting Membracidae (treehoppers - Homoptera) Bugs - secrete honeydew Attracts ants Ants deter predators Female bugs leave early
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SO FAR: Subsociality Aggregations Parental care Without nesting With nesting Solitary nesting Communal nesting
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Parental Care - With Nesting
Nest - parents use or make some structure - lay eggs - provision young Found in - Orthoptera - Dermaptera - Coleoptera - Hymenoptera Dermaptera (earwigs)
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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
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Subsociality in other Orders
Homoptera - aphids Normal nymph “Soldier” nymph
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Subsociality in other Orders
Thysanoptera - thrips Normal female Soldier nymph
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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)
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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
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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
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Eusocial Hymenoptera
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Eusocial Hymenoptera Fertilized 2N Egg (Female[worker]) Unfertilized N Egg (Male[drone])
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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
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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
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Caste Differentiation in Bees
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Caste Differentiation in Bees
Royal Jelly
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Caste Differentiation in Bees
Royal Jelly Hypopharyngeal glands
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Caste Differentiation in Bees
Royal Jelly
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Caste Differentiation in Bees
Royal Jelly Protein Carbohydrate Lipid N D J F A M J J A
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Eusociality in Termites
Reproductive castes Primary reproductives - King + Queen Supplementary reproductives - Neotenics Non-reproductive castes Workers Soldiers
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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)
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Assumption: Subsociality is a necessary precursor for (and primitive to) eusociality BLATTODEA Polyphagidae (including Cryptocercus) ISOPTERA Other families MANTODEA
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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
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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
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Why should a female bee (adult) sacrifice her own reproduction for that of the colony ?
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Kin Selection and Inclusive Fitness
Fitness comes from Your own reproduction Reproduction of relatives Inclusive Fitness
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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
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