For many years now, people in Central Texas have been complaining about difficulty controlling an ant they describe as ‘little black ants’. The primary problem has been that the ants in question may initially respond well to treatment but re-infest quickly.
Some people began to suspect that these might not really be little black ants. These ants are easy to mistake for little black ants with the naked eye (they are about the same size and dark in color), but when viewed through a microscope they are distinctly different.
This is an exotic species that was first reported in the US in the 1970s, as Brachymyrmex musculus, and much of the USliterature refers to it as B. musculus. It is thought to have originated in Argentina, where it was known as B. patagonicus and, because this was the original name, this is now what it is being called here. Although these rover ants have only ‘been here’ for 30 years or so, they are now well established in central Texas.
What do rover ants look like? To the naked eye they look like tiny, dark-colored ants. They are only about 1/16 inch long, or about half as big as fire ants. They are uniformly dark brown and the workers are all similar in size. They do not have a sting. These ants have only one node between their thorax and abdomen, but you have to have a good microscope to see this (Little black ants have two nodes). The node is flattened and angles slightly upward toward the thorax. Rover Ants can also produce winged reproductive “swarmers.” These swarmers are very large in comparison to the worker ants. They are usually found in bathrooms and kitchens and tend to fly toward lights and windows.
Rover ants are common in woods and other natural settings, as well as around buildings. In natural settings they nest in soil or decaying wood. Around structures they are found under stones, landscape rocks and edging, and under/in potted plants. In buildings they prefer areas with high moisture and are often associated with bathrooms or plumbing or structural leaks. These ants nest in small, single queen colonies, but there can be many colonies in an area, and this may be one of the main reasons for the control difficulties. Honeydew from aphids, scales, and similar insects is a favorite food source, but they have to have protein as well.