By: Dr. Kyle Jordan
Because it often nests in or under cracks in pavement, Tetramorium caespitum is commonly referred to as the pavement ant. In nature, this ant generally nests under stones, but it will also establish residence in mulch, walls, wall insulation, under floors, etc. Even if a nest is outdoors, ants may enter structures through expansion joints and natural openings as they forage. Though they have the ability to bite and sting, pavement ants are not an aggressive species. Their status as a pest comes from their habit of foraging for food in homes. Usually they feed on insects, honeydew, seeds and sap, but they will consume a myriad of our foods – especially those with a high fat or grease content.
Since its introduction, the pavement ant has spread from Canada to Florida and across the Midwest. It is believed that this species was brought to the United States in colonial times, in the soil that was used as ballast in merchant vessels from Europe. When the ships arrived at US ports, they would empty the soil and replace it with raw and manufactured goods to take back to Europe.
Pavement ant workers are monomorphic (one form), and range from 1/16th to 1/8th in. long. One queen establishes a colony, but it could eventually have multiple queens producing brood (workers may number as many as 4,000 in a large colony).
Pavement ants are brown-black and have several distinguishing characteristics. The pedicel (the “bridge” from the abdomen to the thorax) is two-segmented. There is a pair of spines toward the rear of the thorax, and there is a pattern of conspicuous grooves on the top of the head and thorax. The thorax is unevenly rounded when viewed from the side; the antennae are elbowed and 12-segmented with a three-segmented club; and a stinger is present.
Winged reproductives typically swarm in June or July, but can emerge at any time of the year – even during winter. The grooves on the head and thorax are also present on the reproductives, and are an important distinguishing characteristic.