I. Classification of Insect SocialityII. AggregationIII. Parental careIV. CommunicationV. Division of laborVI. Evolution of Insect Socialityhttp://research.amnh.org/entomology/social_insects/

Social InsectsSocial Insects

1/3 of the entire animal biomass of the 1/3 of the entire animal biomass of the Amazonian terra firme rain forest is Amazonian terra firme rain forest is composed of ants and termites, with each composed of ants and termites, with each hectare of soil containing in excess of 8 hectare of soil containing in excess of 8 million ants and 1 million termitesmillion ants and 1 million termites

Ivory Coast Savanna: 10 million ants/hectareIvory Coast Savanna: 10 million ants/hectare

Holldobler, B. and E.O. Wilson. 1990. The Holldobler, B. and E.O. Wilson. 1990. The Ants. Belknap Press, Cambridge, MA.Ants. Belknap Press, Cambridge, MA.(for this and next 4 slides)

In most terrestrial habitats, ants are the In most terrestrial habitats, ants are the leading predators of other insects and small leading predators of other insects and small invertebrates.invertebrates.

Leafcutter ants (Leafcutter ants (AcromyrmexAcromyrmex spp. and spp. and AttaAtta spp.) the principle herbivores and most spp.) the principle herbivores and most destructive insect pests in the Neotropics.destructive insect pests in the Neotropics.

Harvester ants (Pogonomyrmex spp. and Harvester ants (Pogonomyrmex spp. and others) are the principal granivores in others) are the principal granivores in deserts of the southwestern United States. deserts of the southwestern United States.

Image: Mark B. DuBois, 2000

In the woodlands of New England, ants move In the woodlands of New England, ants move approximately the same amount of soil as approximately the same amount of soil as earthworms. earthworms.

In temperate forests of New York, they are In temperate forests of New York, they are responsible for the dispersal of nearly 1/3 of responsible for the dispersal of nearly 1/3 of the herbaceous plant species, which are 40% the herbaceous plant species, which are 40% of the aboveground biomass.of the aboveground biomass.

Flow of 13 elements through the Flow of 13 elements through the underground refuse dumps of leafcutters is underground refuse dumps of leafcutters is 16 – 98 times the flow in undisturbed leaf 16 – 98 times the flow in undisturbed leaf litter.litter.

Perhaps 20% of all COPerhaps 20% of all CO2 2 produced in savanna produced in savanna

ecosystems results from termite activity; ecosystems results from termite activity; termites can consume up to 55% of all termites can consume up to 55% of all surface litter in these systems.surface litter in these systems.

Globally, termites probably contribute up to Globally, termites probably contribute up to 20% of the global production of NH20% of the global production of NH44 and 2% and 2%

of the global production of COof the global production of CO22. .

A single honeybee may visit and pollinate A single honeybee may visit and pollinate 1000 blossoms in a single day. In New York 1000 blossoms in a single day. In New York state, which has about 3 million domestic state, which has about 3 million domestic honeybee colonies, each with about 10,000 honeybee colonies, each with about 10,000 worker bees, honeybees could visit 30 trillion worker bees, honeybees could visit 30 trillion blossoms in a day. Wild bees pollinate a blossoms in a day. Wild bees pollinate a number at least equal to that. Thus on a number at least equal to that. Thus on a bright, sunny day 60 trillion blossoms may be bright, sunny day 60 trillion blossoms may be pollinated by the bees in New York, a task pollinated by the bees in New York, a task impossible for man to accomplish today.impossible for man to accomplish today.

Ethiopian proverb:

When spider webs unite they can halt a lion.

Costa, J.T. and F.D. Fitzgerald. 1996. Developmentsin social terminology: semantic battles in a conceptualwar. Trends in Ecology and Evolution 11:285-289

Costa, J.T. 1997. Caterpillars as social insects. American Scientist 85:150-159.

Life cycle of a “typical” ant colony

http://research.amnh.org/entomology/social_insects/ants/ant_colony_cycle.html

Colony starts with a queen that finds a protected place or excavates a nest.

•colony may be founded by 2 or more queens.•queen may receive help from workers of her mother nest•parasitic nest foundation can occur

Queen starts to lay eggs and take care of larvae in the incipient nest.

First generation of workers eclose and take over nest maintenance, colonydevelopment, and feeding of the queen.

Colony passes through a growing phase.

•slave-makers steal pupae from other species

Growing phase may last several years and the colony may end up with millions of individuals living together.

After adequate growth, the colony produces its first generation of sexuals.

•certain species produce apterous queens, and more rarely apterous males

Sexuals produced by colonies of a given region will fly on the same day and at the same time, enhancing their chance to meet in the nuptial flight.

•if there are wingless males or females, there are no nuptial flights; colonies are founded by fission.

On January 30th, after some very hot, stormy weather, while I was at ChevyChase, near Armidale, N.S.W., I crossed the paddock and climbed to the top of Mt. Roul, an isolated, flat-topped, basaltic hill, which rises about 300 feet above the surrounding open, cleared country. The summit, about half an acre in extenet, is covered with low "black-thorn" bushes (Bursaria spinifera). I saw no signs of bull-dog ant nests till I reached the summit. Then I was enveloped in a regular cloud of the great winged ants. They were out in thousands and thousands, resting on the rocks and grass. The air was full of them, but they were chiefly flying in great numbers about the bushes where the males were copulating with the females. As soon as a male (and there were hundreds of males to every female) captured a female on a bush, other males surrounded the couple till there was a struggling mass of ants forming a ball as large as one's fist. Then something seemed to give way, the ball would fall to the ground and the ants would scatter. As many as half a dozen of these balls would keep forming on every little bush and this went on throughout the morning. I was a bit frightened at first but the ants took no notice of me, as the males were all so eager in their endeavors to seize the females.

With the death of the colony queen, the colony is often able to survive just a few months, as queens are not usually replaced inants and the workers are not able to reproduce.

•some species have colonies with multiple queens, in which case the colony persists.

Evolution of eusociality