Linepithema

Ecologically, most species of Linepithema are poorly known. They are reported to nest in trees under bark, in cavities of bamboo, in arboreal ferns, in decayed branches on trees and in rotten limbs on the ground. In contrast, the biology of one species is well known. The Argentine ant, L. humile, is a widespread pest species. It can occur at very high population densities in both urban and rural areas, and has been shown to have a negative impact on local, native plants and invertabrate faunas. This species forms multi-nest colonies with numerous queens and can monopolize resources by rapidly recruiting workers to newly found food sources. In southern Europe this species forms a single colony stretching from France to Italy.

Only a single species of Linepithema, L. humile, also known as the Argentine ant, is known to occur in Australia. It can be very common in both urban and some rural areas, with single colonies having many large nests connected by distinct foraging trails. They are known to cause damage to native plants (Bond and Slingsby 1984) by interfering with the germination and survival of young plants. They can also reduce the numbers of many native ants near their nests by dominating food sources and preventing other ants from feeding or nesting (Ward 1987). With very large colonies and rapid recruitment, they can monopolise food sources before others can find them, or overwhelm those that might have found them first.

In urban areas, these ants can be a significant pest. They establish large foraging trails into houses seeking food and water, and can rapidly recruit large numbers of workers to newly found food sources. They can also establish small satellite nests indoors in potted plants, wall cavities, power points and almost any other small, suitable cavity. Their numbers can be reduced by removing all potential food sources, but generally complete elimination is almost impossible.



Worker of L. humile from Norfolk Island.

Identification
The mandibles with 5 to 8 large teeth and 5 to 13 smaller denticles, and with the first (apical) tooth elongate and much longer than the second (subapical) tooth. The front margin of the clypeus above the mandibles with a broad, shallow concavity.

Linepithema is superficially similar to some Iridomyrmex in overall body shape and colour, but differs in having more teeth on the mandibles, a more tear-drop shaped head (the widest point well above the eyes), the relatively low placement of the eyes on the front of the head, and the weakly concave front margin of the clypeus.

Distribution and Habitats
Australian distribution

Regional Species Lists

 * Australia

Keys to Species

 * Australia