Little Black Ants

Order:  Hymenoptera
Family:  Formicidae
Scientific Name:  Monomorium minimum

The little black ant, as its name implies, is very small in size and black in color.  The adults may have slight brown tones in their coloration.  Although distributed throughout the United States, it is primarily found in the eastern half of the country, and in Southern California and the San Francisco Bay area.

Biology and Habits

In general, higher magnification is needed to accurately identify the 1/16-inch (1.5 to 2 mm) long adult ants.  First, observe where the abdomen is connected to the thorax (that is, the end closest to the abdomen).  The profile of the thorax is unevenly rounded.  Each 12-sigmented antenna terminates in a 3-segmented club.

Foragers can be seen trailing from their exterior nest to foundations and, possibly, entering buildings.  While inspecting for the nest location, pull back lawn thatch or mulch which may hide the trailing ants moving along foundations, and sidewalks, patios or other poured slabs.  Nests are usually constructed under stones and firewood, as well as in open lawn areas where patches of very fine soil have accumulated.  Nests have also been observed under the bark of trees.

In other circumstances, the nest maybe inside a void area behind walls, woodwork or masonry.  The foragers may travel both indoors and outdoors searching for a variety of foodstuffs, such as grease, vegetable materials, sweets, honeydew, plant secretions, and other insects.  Look under the edge of carpet for ant activity.

Little black ants undergo metamorphosis.  Colonies vary in size and may contain several queens.  Workers can relocate the colony, including the eggs and developing larvae, shortly after a disturbance.  The winged reproductives usually appear between June and August.

Control

After accurately identifying the pest ant and locating the trails of ant activity, remove any attracting substrates or foodstuffs.  For example, remove rocks and other debris if activity was located under such items.  Trim branches if the ants are using them to scale up the foundation.  Cracks in the exterior wall require sealing.  If active mounds are located, apply residual insecticides as directed by the label.  Perimeter barrier treatments are seldom needed.

Inside the building, place aerosols or dusts in voids where activity has been noted during the inspection. Another option of control is the use of commercially available baits which are effective in controlling the little black ant.  Perform follow-up inspections after initial bait placement to ensure that the foragers are feeding on the bait and that plenty of bait is available.  Regularly inspect for signs of ant activity to ensure the success of your management program.

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(Courtesy of the National Pest Control Association.)