Pest Information - Ants

There are almost 9,000 species of ants and they can be found from the Arctic Circle to the Tropics. This site will focus on the ants most commonly found in Hawaii. Learn about their Appearance, Habitat, Diet, Type of Damage, and Life Cycle.
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Argentine Ant

Argentine Ant

Scientific Name

Linepithema humile (Mayr) Hymenoptera: Formicidae

Appearance

Argentine ants are small (2.5-3mm) brown ants with a single node in the waist. They are typically found traveling in well defined trails between nests and food sources. Unlike other common small brown ant species, such as the coastal brown ant, Pheidole megacephala (Fabricius), Argentine ants do not have a soldier caste, so all the individuals out scavenging for food are the same size.

Habitat

The population of a colony may vary from a dozen to many thousands and the number of queens from one to hundreds. During the warmer months, satellite nests are usually established close to food sources and these satellite nests are highly mobile, with the workers moving in with eggs and larvae over a short period and abandoning the nest if it is disturbed or the food used up. The adult winged males, which are larger than the workers but much smaller than the winged queens, usually fertilize the queens in the nest and the new queens establish nests nearby after losing their wings. In midsummer and early autumn there is a very large increase in numbers. It has been estimated that infestations grow at a rate of more than 200 meters per year.

Diet

Argentine ants eat a wide range of foods including nectar, insects, seeds, carrion, and honeydew secreted by aphids and scale insects. Workers have a mostly sugar based diet, while larvae and queens feed mostly on protein.

Type of Damage

Because of the nature of the infestation, Argentine ants need to utilize and monopolize every available food source in order to feed the vast numbers of ants that eventually build up in a single infestation. They also compete very effectively with all other ant species, both by fighting and by monopolizing all available food sources. Virtually all other ants are replaced by Argentine ants. Argentine ants become a major domestic pest by invading houses and swarming over foodstuffs, including entering fridges, unopened packets and have even been known to follow the spiral down inside screw-top jars to get at the contents, particularly if the contents are sweet. They invade beds at night seeking moisture and can swarm over sleeping babies, although they are not known to do any harm. Unlike many other domestic pest species, Argentine ants do not nest in houses but nest outside and enter houses in dense trails which can resemble miniature multi-lane highways.

These ants may "cultivate" aphids, scale insects, or mealybugs on fruit trees, houseplants, or ornamental plantings. These sucking insects produce a sweet excretion called honeydew that Argentine ants use for food. Argentine ants also feed on the honeydew-producing insects themselves.

Infestations of mealybugs, aphids, and other sucking pests can damage the health of the affected plant or cause it to become unsightly. Because Argentine ants will harass natural predators to protect their "livestock" they frequently interfere with integrated pest management programs involving biological control. (Biological control is the use of a natural enemy to control a pest organism.) This ant is an important agricultural pest in citrus orchards and vineyards. Argentine ants will also attack and destroy hives of domesticated honeybees.

Life Cycle

The eggs of Argentine ants are elliptical in outline, pearly-white in color, and take from 12 days to nearly 2 months to hatch. The larval stage may be completed in from 11 to 60 days. The pupal period may extend over 10 to 25 days. The minimum period from egg to adult is about 1 month but it may be 4 to 5 months and averages 2-3 months.

Interesting Facts

Argentine ants are a serious threat to the ecosystem. They may eat nestling birds. They out-compete native insects for food and habitat and consume or displace natural predators such as lizards, snakes, and spiders.