The abdominal pedicel contains one segment. The antennae have 12 segments and the scapes (joints) are shorter than the head. The profile of the thorax is not evenly rounded, and the end of the abdomen contains a fringe of hairs. These ants are also called citronella ants because of the distinct citronella odor that is emitted when their colonies are disturbed or when an individual is crushed.
Even though this ant is a common structural pest, there is little information available regarding its general biology. The average colony consists of only a few thousand workers with just one queen. The larger yellow ant nests in rotting wood, in the soil, under stones and in the foundations of structures. It is common in the crawlspaces under houses, and is also often discovered by pest control technicians who dig trenches in preparation for termite treatments. This ant likes to nest in rotting and/or termite-damaged wood.
Larger yellow ant workers excavate soil for their nest galleries. Outdoors, they will pile up the dirt adjacent to their nesting sites, forming unsightly mounds. If there is an infestation under the floor of a building, the ants will move the soil and pile it up into mounds on the floor surface. This can be annoying to building occupants because they will continue to pile the dirt even when it is cleared away.
Dirt will also be thrown out between cracks in the floor and in the walls. Because of the ants’ nocturnal nature, homeowners rarely see them doing this excavation work.
The larger yellow ants feed exclusively on the secretions of other insects. They harvest the honeydew that is produced by subterranean aphids and mealy bugs. These insects are often underground, in rotting logs and under stones, which is why the citronella ants are often in these areas as well.
The day-to-day activities of these ants cause aesthetic problems around structures with piles of dirt. When it is time for the ants to reproduce and expand their colony, a new problem arises. Winged reproductives — both females and males — swarm between spring and early fall. Female swarmers are about 10 mm in length, while the males are considerably smaller. If the ant nest is under the structure, the reproductives will often swarm within the house.