Malacosoma americanum

The larvae of the eastern tent caterpillar are hairy caterpillars, black with a white stripe down the back, with brown and yellow lines along the sides, and a row of oval blue spots on the sides. When fully grown, they are about 2 inches long. They are sparsely covered with fine hairs that are light brown. They can also be identified by the web-like tent they construct in the forked areas of tree branches.

Similar species: Unlike spongy moth caterpillars, tent caterpillars do not have red spots or bristly hairs (Tent catepillars have fine, not bristly, hairs.). Unlike the few other caterpillars that build tents or nests, tent catepillar nests can be found only in spring and are built in the crotch of tree branches. They do not enclose leaves, and larvae feed outside of the nest. As the larvae grow, they increase the size of the tent or nest, which can reach a foot or more in length. Other nest-forming caterpillars enclose leaves in their nests, and build nests in summer or early fall.
 

Range: Eastern North America
 

Common habitats include thickets, fencerows, forest edges, rock outcrops, roadsides, and yards. Nests are seldom seen in forest canopies but they occasionally occur in the understory of open, sunny, woods.
 

Tent caterpillars spend winter as eggs, which usually hatch over one or two days at the time when wild cherry buds are swelling but not quite open; typically in March in much of the range, in late February in the South and in about late April in the North. Caterpillars from one egg mass stay together and spin a silken tent in the crotch of a tree, but caterpillars from two or more egg masses may unite to form one larger colony. The larvae then move to the nearest fork in the twig and construct their first tent there. Eventually, they move to a major fork on a large branch or where a branch comes off the trunk, and make a larger final tent. Unlike fall webworms and most other nest makers, the tent does not enclose foliage, so larvae must leave it to feed. During the heat of the day or in rainy weather, the caterpillars remain within the tent. They emerge to feed on leaves in the early morning or evening, or at night when it is not too cold. 

Because they hatch so early in the spring when it is still cold at night, initial growth is slow. Larvae typically mature about six weeks after hatching. At this time, they usually disperse before spinning a white cocoon. Commonly, a few larvae spin cocoons around the nest, but most spin their cocoons in sheltered spots on trees, under debris, under shingles, or in other protected locations. In about two weeks, the moths emerge. They mate at night, and most females lay their eggs by the second night after they emerge. In places where eggs hatch in mid to late March, the moths generally appear in late May to mid-June. The adults do not feed and are seldom seen except around lights. 

The eastern tent caterpillar is a specialist on a few particular types of fruit trees, native and cultivated. Their favorite food plant is wild black cherry (Prunus serotina), but females often lay egg masses on other species of cherries, plums, apples, crabapples, and hawthorns. The catepillars often completely strip the tree of foliage, but curiously, they will not eat the flowers of wild cherry. The defoliated trees usually grow new leaves in a few weeks, after the tent caterpillars have matured.