tent caterpillar, common name for the larvae of the members of a family of moths (Lasiocampidae), easily recognized by the large silk tents, or webs, that the larvae construct during the spring in the crotches of trees, particularly apple and cherry trees. Tent caterpillars are hairy and usually brightly colored, with blue and yellow spots. Periodically they become serious orchard pests and occur in large enough numbers to defoliate whole trees and damage the fruit. Many larvae live gregariously within the tent, which they use for shelter during the night and in rainy weather. During the day, the larvae leave the tent and feed on the leaves in nearby branches.
The best-known tent maker is the Eastern tent caterpillar, Malacosoma americanum. In addition to being an orchard pest, it has been linked to mare reproductive loss syndrome (MRLS), in which apparently healthy mares experience high rates (more than 70% in experimental studies) of aborted fetuses or stillborn foals. An outbreak of MRLS resulted in the lost of more than 5,000 foals in Kentucky in 2001. Elimination of caterpillar populations, by removing host trees or eradicating the caterpillars, or otherwise avoiding horse contact with the caterpillars and their waste appears to prevent the syndrome. Other species of Malacosoma occur both in E and W North America and have been known to defoliate large areas by attacking a variety of forest and shade trees. Not all species build tents; despite the name forest tent caterpillar, M. disstria, at times an extremely destructive pest that migrates by the millions to new food plants, never weaves a tent.
The tent caterpillar pupates within the oval white cocoon it spins, and the adult emerges during midsummer as a reddish brown or gray, medium-sized, stout-bodied, hairy moth with feathery antennae. After mating, the adult deposits several hundred eggs, covered by a thick, foamy brown crust, in bands around the twigs of the host tree. The eggs overwinter until the early spring when they hatch. Larvae from several egg masses congregate near a fork in a limb and form the tent by crawling about, leaving silk behind. Removing egg masses during the winter or removing tents in the early spring and soaking them in kerosene or burning them, are the most effective means of control.
Tent caterpillars are classified in the phylum Arthropoda, class Insecta, order Lepidoptera, superfamily Bombycoidea, family Lasiocampidae.