The flurry of fine, white hairs on the sides of this caterpillar do not sting, so many people allow it to crawl on their hands and arms. The Eastern Tent Caterpillar looks a lot like the Forest Tent Caterpillar, a close relative. The Eastern Tent larva has a dark head and a solid, creamy white line down its back. The Forest Tent larva has a light head and no creamy line at all. Other colors that make up the overall black Eastern Tent Caterpillar's body include light blue side dots, orange lines flanking the creamy middle one, and fragments of yellow lines and blue specks all along the sides. Over time, the orange and yellow parts may become red, and the white side hairs can turn orange.
This caterpillar is generally found in large groups on trees. Right after hatching in the spring, they collectively begin to build a tent-like shelter of silk at the crotch of tree branches, areas where branches grow out in different directions. The silk tent grows in size quickly, and the fibers are very tough to break. The caterpillars use it for shelter from the elements and predators, and as a launching point for journeys to other feeding areas. Entry and exit holes are usually found at the top, and the broadest side of the tent tends to face east, allowing the early sun to bask on a large portion of the shelter.
Eastern Tent Caterpillars eat the leaves off the tree they started life on, and then they move on to other trees, as a group, once it is defoliated. The caterpillar itself does not hurt people or animals, but it eats more leaves after each instar, potentially stressing trees, especially young ones. The silk shelter is considered unattractive, and the sheer number of caterpillars that may reside in one may bother property owners. For these reasons, measures to physically remove accessible nests may be taken, along with the caterpillars inside it. An easier form of management, if it is deemed necessary, consists of examining branches in winter for egg masses, black foamy clumps that completely surround a branch by a crotch. Pruning that off will reduce the number of caterpillars on that tree. In early summer, look for yellowish pupal cases tucked away in a leaf. They look somewhat like a fuzzy egg, and have wisps of silk around them.
The Eastern Tent Caterpillar is the adult form for this species. It is medium brown and covered in long, soft-looking hairs. Two white lines cross the wings and form a center band that may be lighter brown in color or almost ivory. Pectinate antennae look like bendable hair combs. Adults fly from late spring through summer in areas that have host plants like crabapple, apple, and cherry trees.
The map above showcases (in blue) the states and territories of North America where the Eastern Tent Caterpillar may be found (but is not limited to). This sort of data can be useful in seeing concentrations of a particular species over the continent as well as revealing possible migratory patterns over a species' given lifespan. Some species are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America.*NOTE: States/Territories shown above are a general indicator of areas inhabited by the Eastern Tent Caterpillar. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.