Velvety tree ants get their name from their smooth velvety abdomen. The name of “tree ants” comes from the fact that most species of these ants make their nests in trees.
The California velvety tree ant, Liometopum occidentale (Emery) is one of the most common. The workers are between 1/8″ to ¼” in length. The abdomen is glistening velvety black. The mid-section is reddish and the head is brown. Another species, the pine tree ant, Liometopum luctuosum (Wheeler), is a little smaller and completely dark-colored.
If someone crushes a velvety tree ant worker, it releases an unpleasant odor. The workers also give off that odor if the colony is disturbed. The workers do not sting, but they bite if the nest is disturbed.
Velvety tree ants make their nest in the crooks of trees. Depending on the location, they nest in oaks, sycamores, cottonwoods, and pines. They also nest in the soil under rocks and inside logs or stumps. Colonies are usually very large. Normally the entire colony nests in the same place. However, sometimes there are satellite colonies and the workers move back and forth between the nests.
Velvety tree ants eat honeydew, nectar, and insects. They tend small insects, like aphids, because they produce honeydew. It is common to see velvety tree ant workers moving around in lines or trails on the trunks of trees. They often use tree limbs and branches to enter homes and other structures.
When they move indoors, velvety tree ants often make their nests inside wall voids. The workers often build paper-like nests inside the wall voids. They also hollow out sheetrock and foam insulation for nesting and passages. If they find damp, decaying wood, they hollow it out to nest inside.
Controlling velvety tree ants begins with a thorough inspection. If they have nested in decayed wood, solving the moisture problem will be a priority. If the crawl space is damp, check the vents to be sure they are open and not blocked. A dehumidifier might help reduce the dampness in a basement.
Inspect trees that are near the house for nests or trailing ant workers. Look for openings outside the home that the ants could use as entrances. Make sure exterior doors close tightly and replace missing or damaged weather-stripping Caulk openings around windows and utility openings.
Stack firewood on a rack and move it away from the house. Trim any limbs or shrubs that touch the house. Make sure gutters are clean and downspouts drain away from the foundation.