The pavement ant, Tetramorium caespitum L. is one of the most commonly encountered ants in the United States. The first introduction into the United States occurred from Europe in the beginning of the 19th century. Since then, the ant has become well established and is prevalent in urban areas in the northern U.S. and parts of Canada. While the presence of pavement ants in the U.S. has been acknowledged for decades, the extent of their invasiveness and severity as a pest is not well characterized.
Pavement ants form large colonies, often containing over 10,000 workers. As with most ants, there are distinct castes: one or a few reproductive queens, and a large number of non-reproductive female workers. In early summer, winged reproductive females and males are produced. Mating occurs during nuptial flights in which alate (winged) reproductive ants leave colonies and mate in swarms. Generally, one sex predominates in the reproductives produced by a specific nest of pavement ants (Bruder and Gupta 1972). It takes 42-63 days (at 21-24°C) for a fertilized egg to develop into a worker pavement ant in an established colony, although worker development occurs faster when a queen first starts a new colony (Bruder and Gupta 1972).
Colonies of Tetramorium caespitum are usually monogynous - they are started by a single reproductive queen that carries out all reproduction for the lifetime of that colony - but they occasionally may have two, or possibly more, queens. The majority of nests occupy 1.2-4.8 m2 in area and are 0.45-0.90 m deep (Bruder and Gupta 1972), with multiple crater-shaped mound entrances per nest. Mounds near entrances are not always obvious, as they are built up after rains but slowly collapse thereafter.