The Eastern Tent Caterpillar, Malacosoma americanum (F.), which has been observed in the United States since 1646, periodically at approximately 10-year intervals, becomes so abundant as to defoliate orchards and many species of shade trees.
The insect passes the winter as a small shiny varnished-appearing black egg mass, about ½ inch long, that encircles small twigs. These masses contain several hundred eggs.
The eggs hatch early in the spring as soon as the wild cherry buds begin to break. The caterpillars gather in the forks of the limbs of nearby trees where they construct their tents. These caterpillars do not feed within their web, but congregate there during the night and in rainy weather. They move out of their webs to feed upon the newly opened leaves and in the process may strip off all the leaves from branches near the tents.
As the caterpillars grow, their tents are enlarged. They become full-grown in 4 to 6 weeks, at which time they are about 2 inches long and thinly covered with long, soft, light brown hairs. The general color is black and there is a white strip down the back, bordered with reddish-brown. Along each side there is a row of oval blue spots and brown and yellow lines.
