SOCIALITY IN

INSECTS

Social Insects - Importance

Formica yessensis

- 306,000,000 workers

- 1,000,000 queens

- 45,000 interconnected nests

- 2.7 km2

One colony

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

Oviposition preferences - Corixidae

% on eachsubstrate

Wood Plexiglas Elodea

Subsociality - parental care

- 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 careWithout 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

Some lay only male eggs (workers of Bombus)

Worker sterility

Super reproductive queen

Quasisocial

Semisocial

Sociality among groups of HymenopteraApinae

Megachilinae

Adreninae

Colletinae

Halictinae

Crabronidae

Sphecidae

Other vespoids

Formicidae

Scoliiidae

Eumeninae

Stenogastrinae

Polistinae

Vespinae

Chrysidoidea

Rest of Apocrita

solitary

eusocial

subsocial

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

-distribution of protein-rich food to larvae

-distribution of carbohydrate-rich food to adults

-clean cells and dispose of dead larvae

-ventilation and air-conditioning of nest

-nest defence

-foraging - wood pulp, fluids, prey

-construction and repair of nest

YOUNG

MIDDLE AGE

OLD

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

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Conclusion: These animals represent an evolutionary precursor toIsoptera (termites)

Assumption:Subsociality is a necessary precursor for (and primitive to) eusociality

ISOPTERA Other families

Polyphagidae(including Cryptocercus) MANTODEA

BLATTODEA

Termitidae - Pathways for Caste Development

King + Queen

egg

Larva (1st)

Large larvae (2nd)

Large worker 1

Large presoldier

Large worker 2

Large worker 3

Large worker 4

Large worker 5

Large soldier

Small larvae (2nd)

Small worker 1

Small worker 2

Small presoldier

Small soldier

Nymph 1

Nymph 2

Nymph 3

Nymph 4

Nymph 5Alate

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

Pseudergates develop into reproductives

No change

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

-have 1/2 of mother’s genesFull sisters share 3/4 of their genes

Workers are more related to each other than their mother