Ants are insects that belong to in the order Hymenoptera, along with bees, wasps and sawflies. Ants belong to the family Formicidae. Scientists believe ants evolved from wasps in the Cretaceous Period, about 110 million years ago. The earliest fossil ants have been found in North American amber, which has been dated at 94 million years old.
An ant is composed of four distinct body parts (tagma).
Ants have a holometabolous (complete metamophosis) life cycle. After hatching from an egg, ants begin life as larvae. The differentiation of the female castes (into queen and worker sub-castes) is largely determined by environmental factors such as:
Males usually develop from unfertilised eggs.
Workers are the most numerous ants in a colony. Workers are wingless, (usually) sterile females. The first workers in a newly established colony (nanitics or minims) are usually smaller and more timid that those from a more mature colony of the same species. In many species, members of the worker caste of are all of the same size and shape (monomorphic). In some species two worker sub-castes exist - minors and majors - that are distinctly different in size and shape (dimorphic). In others there is a continuous gradation in size between minors and majors (polymorphic).
Workers can be predators, scavengers or farmers tending 'flocks' of aphids or harvesting seeds from plants. Minor workers perform tasks suck as grooming, brood care, and caring for the queen. The major worker roles are concerned with nest defences, carrying dead nest mates outside, and cutting large food items into smaller pieces, some even act as food storage vessels.
Workers generally live one to three years depending on the species and climate.
Queens are similar in overall appearance to the workers. They are larger, the altitrunk has more sclerites on to allow for flight muscles and wings, and the gaster is larger to allow for large ovaries.
After establishing the colony the queen produces eggs and regulates the activities of the colony through hormonal control.
Queens usually live much longer than the workers, some species having been kept in laboratory nests for up to 29 years.
The males are very similar to wasps in appearance and are usually smaller than the female castes. They have small heads with poorly developed jaws and large ocelli (simple eyes on top of head). Males generally live only for a few weeks and die within a day or two of leaving the nest on nuptial flights.
Most ants are general predators or scavengers. Solid prey, which is most often seen being carried by workers, is intended as food for the larvae.
Adult ants feed exclusively on liquid foods. They collect these liquids from:
Returning foragers pass the liquid food to other adults, especially those that remain in the nest (such as the queen), in a process called trophallaxis. Trophallaxis occurs when liquid food that is stored in the forager's crop is regurgitated for nest mates on demand.
Communication between members of a colony is almost entirely chemical, with some tactile communication.
Ants use pheromones to:
Tactile communication is mainly used as requests for food between adults.
Copyright © Australian Museum, 2003
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