Pest Identification

Size:
Argentine ant workers are about 1/16 in (2.2-2.6 mm) long. Queens are about 1/8-1/4 in (4-6 mm) long.

Color:
Light to dark brown

Where found:
Native to Argentina and Brazil, but probably brought to U.S. on coffee ships before 1891. Now found in southern U.S. and in California, with isolated infestations in Illinois, Maryland, Missouri, Oregon and Washington.

Habitat:
Argentine ants build shallow nests near a source of moisture, such as along sidewalks, under rocks, between plants, near water pipes, potted plants.

Food:
Argentine ants follow regular trails, and are often found outside near insects such as aphids, that produce a honey-like secretion, called honeydew. They like sweets best, but also feed on oil, fats, and meat. 

Biology:
Colonies have many queens, and hundreds, or up to several thousand, workers. The numbers change depending upon the time of year. Over wintering nests are formed by colonies joining together. Different colonies get along with each other, but Argentine ants are aggressive towards other ant species and usually get rid of them. Mating takes place in the nest, so winged reproductive females are not often seen. Development from egg to adult takes an average of 74 days. 

Damage:
Argentine ants are mainly a nuisance pest, but since they crawl over garbage, sewage, and carrion, they can transport disease organisms.

Invasion:
Argentine ants come inside when the weather is very wet or very dry, and when they are short on honeydew.