Ants are one of the major subgroups of the insect order Hymenoptera, which also includes wasps and bees. Most species are distinguished by one or two small segments that separate the middle of the body (mesosoma) from the main part of the abdomen (gaster).
There are about 15,000 described species worldwide. Most of the world’s ants are found in moist, warm habitats.
There are four stages in the life cycle: egg, larva, pupa, and adult. The cycle usually lasts from six to 10 weeks. Some queen ants can live for up to 29 years, and some workers for up to seven years. Males usually live only a few weeks, and die shortly after their mating flight.
Ants are social insects, living in colonies ranging from around 100 in the case of New Zealand’s ancient Amblyopone species, to well over a million for the introduced Argentine ant Linepithema humile.
A colony consists of queens, males and workers (wingless females). The males have wings and fly in swarms with young queens. Once they have mated, the queens drop to the ground. They chew or break off their wings, and dig a small hole where they lay their eggs and start a colony.
Fertilised eggs produce female ants – queens and workers. Unfertilised eggs produce male ants.
Ants are mainly scavengers and general predators, eating fats, sugars, oils and protein. Solid food is carried back to the colony for the larvae. However, adult ants feed only on liquids taken from their prey (which includes living and dead invertebrates), from sap-sucking bugs and from plant glands.
Some species have a strong preference for sweet foods while others, like the large-headed Pheidole species, prefer fatty and oily foods.
One native New Zealand species, Discothyrea antarctica – like other Discothyrea species – probably preys specifically on the eggs of arthropods (insects, spiders and the like).
The introduced Australian ants Orectognathus antennatus and Strumigenys perplexa have long, projecting jaws that act like spring-traps. These ants eat springtails (primitive insects of the genus Collembola) and small, soft-bodied soil animals.
Queens and workers may have a sting to defend themselves and subdue prey, or a ‘spray nozzle’ through which they squirt formic acid. Depending on the species, the sting can be mild to very painful. Some will bite as well.