The pavement ant, Tetramorium caespitum, is a common household pest. Its name comes from the fact that colonies usually make their homes in pavement. It is distinguished by one pair of spines on the back, two nodes on the petiole, and grooves on the head and thorax. The species is native to Europe, but was introduced to North America in the 18th century.
The pavement ant is dark brown to blackish, and 2.5–4 mm long. Like other ants there are the workers, alates, and a queen. Alates, or new queen ants and drones, have wings, and are twice as large as the workers.
The drone's only job is to mate with the queen, and reproduction is at its highest in spring and summer. Tetramorium, like many other ants have nuptial flights where drones fly high up in the air and mate with new queens. The queen finds a suitable nesting location and digs a founding chamber. As the eggs hatch and the ants develop they will spend that time, about two to three months, tending to the queen of their colony. They will continue helping in the colony until they are a month old.
Pavement ants are opportunistic feeders that will ‘swarm’ on foods within their foraging range. Outdoors, this ant feeds on insects, honeydew, seeds, and plant sap. Once inside your home, they will feed on meats, nuts cheese, honey, breadcrumbs, meats, and grease.
During early spring, colonies attempt to conquer new areas and often attack nearby enemy colonies. These result in huge sidewalk battles, sometimes leaving thousands of ants dead. Because of their aggressive nature, they often invade and colonize seemingly impenetrable areas. In summer time the ants dig out the sand in between the pavements to vent the nests.
Pavement ant colonies are fairly small and contain several queens. Outdoors, these ants nest in soil, under stones, by slabs next to buildings, and in pavement cracks. Once inside your home, they will occasionally nest in walls, insulation, and under floors. Colonies will move near a heat source in winter, and will often follow pipes through slabs to access buildings.
Control of foraging pavement ant workers can be accomplished through the use of baits. The workers carry the baited material back to the nest, eliminating the colony. Many different types of bait are available to the homeowner in this regard. However, baits containing hydramethylnon, fipronil or boric acid are slower acting and do not kill the workers before they have had a chance to share the baits with the queen and developing immature ants. Place the baits in areas where ant activity has been observed and make certain that children or pets cannot reach them. Maintain sufficient amount of baits to satisfy the colony by replacing used baits. It may require two weeks or longer to obtain control.
Pavement ants often enter buildings through expansion joints in slabs. Application of insecticides through these cracks may help in controlling the colony beneath. In severe infestations, a slab floor may need to be drilled and treated by pumping chemical underneath with a specially equipped sprayer.
Some photos and information are provided by Bayer.
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