Carpenter Ants

Source: IDPH Website

Carpenter ants are one of the most common household pests in the Midwest. Besides being a nuisance indoors, these ants damage wood by hollowing it out for nesting space. While carpenter ants do not eat wood, large colonies can be destructive; however, are more of a nuisance than a threat to structural integrity.

Carpenter ants are the largest pest ants in the United State. The black carpenter ant (Camponotus pennsylvanicus) is common in the Midwest. The typical adult, known as a “worker” ant, is black, wingless and varies from ¼- to ½-inch in length. The size and color of carpenter ants vary considerably between species and even between ants from the same colony, so these features cannot be relied upon for identification. Instead, look first for the carpenter ant’s smoothly rounded thorax (viewed from the side) and single node (the small triangular connection between the abdomen and thorax; some ants have two nodes).

Carpenter ants are fast moving and stop only to feed or share food with other ants. They are most active at night. Workers emerge from the nest about 15 minutes after sundown. Like other ants, they follow chemical trails in search of food -- sometimes hundreds of feet from the nest – and often create permanent, well-beaten trails like cow paths through the grass. A colony may use the same path from year to year.

A mature carpenter ant colony may contain as many as l0,000 individuals. Typically, only 10 percent to 15 percent of the workers are outside the nest searching for food including insects and a variety of human foods such as meats and sweets. Other workers engage in nest construction and repair, colony defense, and feeding and caring for the larvae, pupae and queen. The workers’ variation in size enables them to specialize for different tasks.

Each year, carpenter ants become active in the spring (March-April) and remain so through early fall (September-October). A mature carpenter ant colony usually releases reproductive individuals in springtime. The reproductives have wings and, like winged termites, are commonly known as “swarmers.” The swarmers’ purpose is to mate and, in the case of females, to fly to a new location, lay eggs and establish a new colony. In winter, most carpenter ant colonies become dormant, although indoor nests may show some continued activity.
Carpenter ant nests consist of smooth, clean tunnels and excavations in wood that run with or against the grain. In contrast, subterranean termite tunnels are lined with a mud-like material and always run in the same direction as the wood’s grain.

A carpenter ant colony is often composed of a series of nests. The main nest, or parent nest, is usually located outdoors, often in woodpiles, logs, stumps, or trees – sometimes several feet above the ground. The nest contains the queen, some workers, larvae and pupae. It may be joined by sub-nests, or satellite nests, containing workers, and older larvae and pupae. The colony’s reproduction takes place in the parent nest where the queen lays eggs. Larvae hatch from the eggs, are cared for and later may be transported to satellite nests. There, the larvae will undergo pupation and complete their metamorphosis to become adult workers.
It is the satellite nest that is most often encountered in structures. A satellite nest is often established in an area where wood has become moist. Common sites include wood around leaking chimney flashing, attics, skylights, bathtubs, windowsills, doorframes, porch supports, columns, soffits, wood siding and shingles, and flat roofs. Carpenter ants also will nest in fiberglass and foam insulation.

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