Many moth caterpillars congregate in large numbers, leading to the general name ‘armyworm’. The armyworm that concerns farmers is a cutworm that lives on the ground, feeding on agricultural foragecrops.
People also often refer to some forest insects as ‘armyworms’. These caterpillars may congregate and feed in large numbers on hardwood trees. However they are distinctly different.
Eastern tent caterpillar
Congregate in a silken tent and feed on trees such as cherry and apple. Note the white line down its back
These caterpillars feed on many hardwood trees. They also congregate on trees, especially oak, poplar, birch and apple. Note the five pairs of blue and six pairs of red dots, and its hairy body.
