Every year around this time, at least a handful of questions come in about hairy caterpillars. By September, various species of tussock moths (Family: Erebidae, Subfamilies Lymantriinae and Arctiinae) have mature caterpillars that garner a lot of attention due to their colorful and hairy appearance. The following are a few (but not all) examples:
The rusty tussock moth (Orgyia antiqua) may be found in woodlands, fields, and forests in New England with mature caterpillars present in August and September. This species is a generalist feeder. Host plants include alder, apple, cherry, elm, fir, hemlock, larch, maple, oak, pine, poplar, spruce, viburnum, and willow, among others. Mature caterpillars have a jet black stripe down the dorsal side, four straw-colored tufts of hair, and bright red warts.
The definite tussock moth (Orgyia definita) are also found in fields, woodlands, and forests in New England, but caterpillars may be present from April to September. Another generalist, caterpillars will feed on the foliage of basswood, birch, blueberry, elm, hackberry, maple, oak, willow, witch hazel, and other woody plants. This particular species is usually quite common. Caterpillars are mostly bright yellow with cream to yellow tufts of hair and a colorless or grey dorsal stripe and yellow warts.
The white-marked tussock moth (Orgyia leucostigma), found in the same habitats as the previous two species, can have caterpillars present in New England until November. This generalist feeder uses apple, birch, black locust, cherry, elm, hackberry, hickory, oak, rose, willow, fir, hemlock, larch, spruce, and other conifers as hosts. Caterpillars have a bright red head, four white – yellow tufts of hair, a black dorsal stripe surrounded by yellow dorsal stripes on either side, with red glands elsewhere on the body. These caterpillars can be occasional pests of Christmas tree plantings. The white-marked tussock moth, like many tussock moth caterpillars, may cause allergic reactions in certain individuals if their hairs come into contact with sensitive areas of the skin.
Another commonly seen caterpillar this time of year is the hickory tussock moth (Lophocampa caryae). Caterpillars may be present in July, August, and September. Host plants include birch, quaking aspen, basswood, and black locust, among others. Caterpillars are mostly white, with a black stripe down the back and sporadic longer black hairs or “pencils”. The hairs from the hickory tussock moth can also cause allergic reactions in some individuals.
While these native caterpillars do not typically reach densities that cause defoliation and dieback of their host plants, occasional outbreaks can occur. In the meantime, a good rule of thumb for interacting with hairy caterpillars is to give them their space. While not all hairy caterpillars cause allergic reactions in all people, some can cause particularly severe reactions. Examples include the browntail moth (Euproctis chrysorrhoea) and flannel moth species in the Family Megalopygidae, among others. Therefore, exercise caution and resist the urge to pet hairy and fuzzy looking caterpillars when you see them.
Looking for more information about the beautiful caterpillars that call Massachusetts home? A great guide to some of our most common species is Caterpillars of Eastern North America by David L. Wagner (2005).
Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program