Adult eastern tent caterpillar moths are brown with 2 light-colored bands cutting across the forewing. Sometimes, the middle band between the two lines is lighter or whitish. Like others in their family, these moths are medium-sized, with thick, long scales that make them look furry. Both males and females have feathery antennae. Females are paler and more yellowish, and larger, with more rounded wings.
Caterpillars are much more easily seen than the adults. They live in groups in “tents” made by innumerable silken strands in the crotches of host trees. The caterpillars have long, pale hairs; the body is mottled and striped with blue, yellow, and black, with a whitish line running down the back. The head is dark.
Similar species: The closely related forest tent caterpillar (M. disstria) looks very similar, but adults have dark (not whitish) lines on the forewings. The larvae do not have an unbroken line along the back; instead, there is a light-colored mark on each segment down the back — the shape of each mark is like a keyhole, shoeprint, or bowling pin. Also, the communal larvae of that species do not create tents. Instead, they only build silken mats and guidelines on trunks and branches that guide them to and from feeding locations and group gathering sites.
Habitat and Conservation
Caterpillars are reported on a wide variety of host trees, especially trees in the rose family: apple, cherry, peach, plum, crabapple, and so on. Thus they eat both native trees as well as cultivated orchard and landscaping trees.
The adult moths do not eat, for their mouthparts are undeveloped or lacking. In fact, females of this moth family emerge from pupation with all of their eggs fully developed, so they do not need to acquire additional nutrients for growing their eggs.
Populations of this species rise and fall in a cycle, with their numbers growing for a number of years, then “crashing” before starting the cycle again.
Not many birds prey on eastern tent caterpillars. With their hairs and striped black and yellowish pattern — especially striking when they are grouped together in a mass — they send a visual warning of toxicity. Indeed, the cherry leaves that they typically eat contain cyanogenic chemicals, and when disturbed, the caterpillars can vomit cyanide juices at their predators. The caterpillars also thrash around the fore part of their bodies when disturbed, which usually causes all their neighbors to join in. The entire wriggling mass is also a predator deterrent.
In years when eastern tent caterpillars are especially numerous, they can chew away most of the leaves on their host trees. This forces the tree to grow a new set of leaves, which is stressful to the tree. Healthy, mature trees can withstand this, but if another stress occurs soon after, such as prolonged drought or disease, it could result in tree death.