Hatched larvae are less than 1.2 inches long and usually black in color.  They linger around the egg cluster for several days if the weather is cool or rainy, then climb trees or other objects, trailing silken threads as they move.  When the larvae reach the top, they do not feed but drop on silken threads and are dispersed by the wind.  Feeding at night for 4 to 6 weeks, large larvae generally rest during the day unless populations are very large, then they wander constantly.  They continue to feed, shed the outer skin and feed until they are about 2 inches long.

Gypsy moth caterpillars hatching in early May.

The egg masses are intertwined in a matting of hair from the body of the female.  The hair is a tan-buff color.  It is also very water repellent and a good insulator.  These egg masses range in size from one to three inches long and are sometimes tear dropped in shape.  Each egg mass can contain from 50 to 1,500 eggs.  Hatching occurs around the first of May and coincides with the time tree buds start to open.   This stage lasts for 7-10 days.

Gypsy moth caterpillars feeding on foliage.

During the stationary stage the larvae are changing into moths.  This generally occurs from the end of July until early August.  After about 10 days in the dark colored pupa cases, the adult moths emerge, leaving the pupa cases  behind.

Large Pupae-Female Small Pupae—Male

The female moth is creamy white and does not fly but emits a chemical called a pheromone to attract a male moth.  The male is brownish and flies in a zigzag pattern looking for a female.  A single male can mate with many females.  Both sexes have chevron markings (v or notch-shaped markings) on each forewing.

Male and Female gypsy moth on an egg mass