The eastern tent caterpillar (Malacosoma americanum
) is a moth species native to forests of North America. It is at the caterpillar stage that the average person would happen along this species. The caterpillars are social, and in the early spring a cohort of newly hatched caterpillars (typically between 50-200 individuals) build a silk tent together, in which they live during their larval phase. As they grow in size, the caterpillars continuously expand the tent, and these conspicuous silky structures are easily viewable in crooks of tree branches in the spring. Caterpillars feed together three times a day, at dawn, evening, and night, following silk threads that they spin from their tent to distant feeding sites, and then return en masse along these silk trails to rest in their nest before feeding again. Caterpillars also release pheromones to mark trails directing the colony to good feeding sites. Their preferred host plants are cherry, apple and rose species but they are also commonly found on other broad-leaf trees and shrubs, such as ash, birch, will, maple, oak and poplar. Adults are small, grey and inconspicuous moths, and do not feed. A colony of Eastern tent caterpillars can quickly defoliate small ornamental trees, but trees usually recover with a new growth of leaves later in the year, since the species is univoltine (only has one generation per year). Populations fluctuate from year to year and bloom in outbreak numbers every several years. Heavy M. americanum
infestations can cause serious damage to larger trees. Eastern tent caterpillars are considered a pest for aesthetic reasons, and also a major pest to apple orchards, where it is the subject of pest-management systems. Eastern tent caterpillar is not effectively controlled by pesticides. Natural enemies are important to managing population numbers, and mechanical removal of nests can greatly reduce the problem. Although the exact cause is still unclear, Malacosoma americanum
caterpillars are believed responsible for Mare Reproductive Loss Syndrome (MRLS), a syndrome in which mares exposed to eastern tent caterpillars show increased incidence of fetal loss.
(Sebastian et al. 2008; Wikipedia 2011