Mysterious Yellow Moth

My husband spotted a vivid yellow crawler in our holly bush. At first, we thought it was a piece of yarn, but upon closer inspection, we saw the fuzzy object was a caterpillar. Will you help us identify it?

—Virginia Brumbaugh, Brooklyn, Connecticut

Tom: The caterpillar your husband photographed is actually a moth, known as the spotted apatelodes (Apatelodes torrefacta). You can easily identify these crawlers by their red prolegs. The caterpillars can be yellow, like this one, or also white with black tufts. They feed on a variety of trees, from cherries and maples to walnuts, willows and many others. The creature is part of the American silkworm moth family. As a moth, it is a grayish color and often flies between June and August.