More than 11,000 species of caterpillar are native to the United States. They are the larval stage of insects belonging to the order Lepidoptera, which is largely made up of butterflies and moths. Caterpillars come in a number of forms, colours and sizes. While many caterpillars have completely smooth bodies, others bear tubicles, bristles and spines, which identify them as "hairy" caterpillars. These caterpillars can occasionally sting or cause skin irritation, but are usually harmless.
Eastern Tent Caterpillar
Malacosoma americanum, or the eastern tent caterpillar, is largely limited to the southeastern United States. Adult larvae reach two inches in length and are predominantly black, but with red hairs running along each side of the body. They are considered pests due to their habit of building silken nests in fruit trees, which may be completely defoliated if the species is present in large numbers. The population fluctuates yearly, depending on the impact of diseases and predation by wasps.
The caterpillar of the walnut moth, Datana integerrima, is found in various parts of the southern and eastern United States and from Ontario, Canada down to northern Mexico. The body of a full-grown larva is black, but covered with an abundance of long white hairs. These caterpillars range between 1-2 inches in length. They are quite common insects in the hardwood forests of the eastern United States, where they are known to cause considerable defoliation to trees.
The milkweed caterpillar, or Euchaetes egle, is also called the milkweed tussock moth. Its hairy body is heavily black in background, but fused with bright orange and white tufts on its back. This colouration has given rise to another name; tiger moths, and advertises to predators that the insects carry a dangerous toxin. The milkweed part of its name comes from the type of thick foliage that they rely on for food. Groups of milkweed caterpillars are known for stripping entire patches of milkweed in the eastern and central United States bare.
Isabella Tiger Moth
Not to be confused with the milkweed "tiger," the caterpillar of the Isabella tiger moth, Pyrrharctia isabella, also goes by the name woolly bear. This species is found all over the United States where they are most commonly observed between spring and fall. They are densely coated with thick black hairs at the front and back of their bodies and a broad band of red in the middle. They feed on grasses and weeds, including dandelion and nettles.