Ant, Australian

Nothomyrmecia macrops

phylum: Arthropoda

class: Insecta

order: Hymenoptera

family: Formicidae

status: Critically endangered, IUCN

range: Australia

Description and biology

Biologists (people who study living organisms) have identified about 9,500 species of ants (the actual number of ant species on Earth may be two or three times that many). The Australian ant, also known as the dinosaur ant, is considered one of the most primitive ants alive. Workers measure approximately 0.4 inch (1 centimeter) long and are golden yellow. They have long jaws and a single waist node (narrow area where the abdomen attaches to the thorax or chest). Their stings are very strong and effective. The ants have a sound- producing organ on their abdomens that they use to create a barely audible chirp. In related ant species, this organ is located on the back.

Australian ants emerge from their nests shortly after nightfall to forage for insects. They do not return to their nests until just before dawn. Biologists believe most ant species use scent markers to navigate. As they travel above ground, ants

lay down a chemical from a gland located at the tip of their abdomen. After they have collected enough food, the ants return to their nests by following these odor trails.

An ant colony is an all-female society. Queens are winged females who produce young. Workers, soldiers, and other specialized members of a colony are all wingless, infertile females (these are the ones normally seen traveling above ground). The only function of winged males is to impregnate or fertilize virgin queens. Once they have done so, these males die. Once a queen has mated with numerous males, she stores the sperm and returns to the nest. She then lays her eggs. Those eggs that are fertilized with the sperm develop into females. Unfertilized eggs develop into males. Females become queens or workers depending on the type of food they are fed during their larval (immature) stage.

In Australian ant colonies, virgin queens and males are produced in late spring and early autumn. Although biologists have not witnessed mating activity, they believe the queens and the males leave their colonies in late summer to mate in flight.

Habitat and current distribution

Australian ants are found only in the Australian state of South Australia. They occupy several sites in an area measuring less than 0.4 square mile (1 square kilometer). Their total population number is unknown.

These ants prefer to inhabit woodlands dominated by tall eucalyptus trees. The ground in these areas is covered with a thin layer of leaf debris. Few herbs or grasses grow there. Nests are located underground and have concealed entrances.

History and conservation measures

Biologists originally believed this ant species had inhabited only Western Australia. Specimens had been collected there in 1934. In the years following, the ant could not be found. In 1977, a site was discovered in South Australia, but it was destroyed shortly afterward when workers laid an underground telephone line in the area. Since then, three other sites have been discovered nearby.

Habitat destruction is the major threat to this ant. Human populations are increasing in the Australian ant's limited range. Fire is also a concern. Bush fires at night could kill large numbers of foraging workers, thus wiping out a colony.