carpenter ant

carpenter ant, (genus Camponotus), genus of more than 1,000 species of ants known for nesting in dead or decaying wood. Carpenter ants are found nearly worldwide in most terrestrial habitats and are particularly dominant in rainforest canopies. Ecologically, carpenter ants play an important role in the decomposition of dead wood and are an essential element in the food webs of many ecosystems. Economically, they can cause extensive damage to human-built structures, and living trees with carpenter ants inside are sometimes more vulnerable to wind damage.

Physical description

Depending on the species, carpenter ants have smooth or hairy black, yellow, brown, tan, reddish, or black and red bodies, which consist of a head with elbowed antennae, a thorax with a constricted waist, and a rounded abdomen. They do not sting. Like other ant species, each carpenter ant colony has three castes: fertile queens, infertile female workers, and male drones. Queens are up to 20 mm (0.8 inch) in length, and drones are smaller. The several types of workers vary in size. The largest workers, called majors, can be up to 12 mm (0.5 inch) in length and serve to defend the colony and forage for food. The smallest workers, known as minors, excavate the nest and tend to the colony’s larvae and pupae. Some species, such as Camponotus rufipes, C. herculeanus, and the Japanese carpenter ant (C. japonicus), have an intermediate-sized worker, known as media.

Carpenter ants are among the largest and most common ants in North America. Species of carpenter ant found in this region include the black carpenter ant (C. pennsylvanicus) and the western black carpenter ant (C. modoc). 

Natural history

Carpenter ants are eusocial insects with a highly complex society that cooperates almost as a single unit. Each colony is founded by a single mated queen, who excavates a small nest and sheds her wings. Most species make their nests in dead standing trees, the dead interior of living trees, or tree stumps, although some species make nests in soil. Having selected her nest site, the young queen lays small, white, oval-shaped eggs and tends to them herself. The eggs hatch and develop into white, legless larvae that resemble fat worms or grubs. The larvae develop into white- to tan-colored, capsule-shaped pupae with the antennae and legs folded against the body. The pupae develop into adults: the first workers of the new colony.

To support the queen in her sole responsibility of egg-laying, the first workers take over all other duties of the colony, including foraging for food and excavating new tunnels and galleries to enlarge the nest. Unlike termites, carpenter ants do not consume wood; instead, they use their strong mandibles to tunnel into wood, then push the debris outside the nest. As the colony grows, the workers establish satellite nests in drier wood for older larvae, pupae, and other workers. A large colony can develop in three to six years. After several years, winged virgin queens and male drones are produced in late spring to midsummer. After they are fully developed, they fly in nuptial swarms and mate in midair. The males die, and the mated queens then search for appropriate sites in which to found their own nests.

Carpenter ants are omnivores that often forage at night. They consume sweet substances, such as flower nectar and honeydew, a waste product excreted by aphids that consume plant sap. In addition, carpenter ants eat both live and dead insects and will scavenge human food.

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Zombie-ant fungus

The zombie-ant fungus (Ophiocordyceps unilateralis) is a largely pantropical fungus that primarily infects carpenter ants. The fungus gains access to an ant when its sticky spores attach to the insect’s body. The spores send out hyphae that penetrate the ant’s exoskeleton, eventually manipulating the insect’s movements. The fungus consumes the ant from the inside out and finishes by erecting a stalk that releases spores from the ant’s head.