Most visible members of this species are about 1/8-inch in length. Their color varies from dark brown to black, and the body is often shiny in appearance.
Colonies of Argentine ants can grow quite large and contain tens of thousands of workers and numerous queens. Each colony will be divided into subcolonies located in various suitable harborages connected by established trunk trails. These subcolonies can number from a few hundred to thousands of individuals. Since members of two separate colonies are not aggressive toward each other, colonies will often combine with one another. This creates huge super-colonies that may extend over several properties. Argentine ants are very aggressive and will drive out native species of ants creating an environment where they are literally the "king" of the anthill. Their primary food source during the warm months is the sweet "honeydew" produced by aphids and mealybugs. The presence of fruit trees, roses, and other plants that attract aphids often contribute to Argentine ant infestations. Argentine ants reside outdoors, usually in shallow nests in the soil beneath a stone, board, or any other item that provides protection. Small, medium or large subcolonies will locate themselves in piles of lumber, bricks, or debris, in landscape mulch, in river rock; within and under insulation; and in wall voids or any other suitable void. Argentine ants are becoming very common invaders of homes in the Southwestern United States. The Argentine ant can be very difficult to control.