Spongy Moth One Year Life Cycle

Life Cycle Calendar

  1. Calendar for Homeowners (PDF)

Click here to watch a video by UMass Extension about the gypsy moth life cycle.

September - May * Embryo and Diapause Stage

A single egg mass is intertwined in a matting of hair from the body of the female. This hair is tan-buff in color, very water repellent, and a good insulator. Masses range in size from 1 to 3 inches long and are sometimes tear dropped in shape. Once the egg mass is produced each egg's embryo immediately starts developing and in a month, the tiny larva is fully formed and ready to hatch. At this point, however, the larva goes into diapause becoming insensitive to cold. An egg mass may contain from 100 to 1,000 eggs. Hatching occurs about the first of May and coincides with the opening of tree buds. 
Gypsy Moth Orange Egg Mass

Mid - Late May * Hatching Stage

Newly hatched larvae are less than 1/8 inch long and usually black in color. They may linger around the egg mass for several days if the weather is cool or rainy.  The larvae 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. This behavior is called ballooning.  Once ballooning is done the larvae begin feeding.  Hatching and ballooning may last for 7-10 days.
Dozens of Hatching Caterpillars

June - Early July * Larval Feeding Stage 

During the larval stage the caterpillar will molt, shedding its exoskeleton (5 times for a male and 6 times for a female).  Each molt is called an instar. A single caterpillar eats an average of one square meter of foliage during this stage.  Fourth instar caterpillars are identified by a beige head and dark marks, 5 pair of blue dots followed by 6 pair of red dots down their backs. Large larvae feed at night and generally rest during the heat of the day unless populations are very large, then they wander constantly. They continue to feed, molt, and feed until they are about 2 1/2 inches long.  
Gypsy Moth Caterpillar

Late June - Mid July * Pupal Stage

During this stage the caterpillar looks for a protected place where they will be safe from enemies like mice, birds, and parasitic wasps to pupate and change into a moth. The caterpillar sheds its skin and its new skin is a dark, reddish-brown color usually attached to a tree trunk, rock, or other sheltered place by a loose net of silken threads.  This generally occurs from the middle of July until early August. After about 10 days of metamorphosis the adult winged moth emerges, leaving the pupa cases behind.  Female pupae are larger than male pupae.
Pupa Stationary Larvae

July - August  *  Mating & Egg Mass Laying Stage

The adult female and male moths look very different from each other. The female is larger than the male and is creamy white with black "V" markings on her fore-wings.  Female moths cannot fly; she attracts a mate by emitting a powerful pheromone.  Males are a mottled brown and gray and have large feathery antennae. They are similar in appearance to many native moths. They can be distinguished, however, by their behavior, as they fly in search of females in the late afternoon; not at night. Males pick up the scent of the female pheromone with their antennae. The male flies in a zigzag pattern toward the source of the pheromone.  Once he locates the female, he communicates  by dancing over and around her while rapidly beating his wings and then the pair mates. Shortly after mating the female deposits her eggs in a single mass and covers it with the yellowish-tan colored hairs from her own body. The only function of the adult stage of the gypsy moth is to reproduce leaving behind as many as a thousand descendants.  Unlike many other moths and butterflies, the adult gypsy moth cannot feed.  The moth has about 2 weeks to find a mate before death; completing their one year life cycle.
Male and Female Gypsy Moths