Gypsy Moth

The gypsy moth is the most damaging exotic species ever to be introduced to North America. The Gypsy Moth's ability to eat more than one (1) square meter of leaf foliage during its caterpillar stage has defoliated millions of acres of trees and shrubs since being brought to the United States.

From May to mid July is when we find gypsy moth caterpillars in Roscommon County. Lots of people in the county have found gypsy moth caterpillars on their property this year. (See the one smgrose posted in the project on June 18.) This is when caterpillars are feeding heavily, and we see lots of defoliation, leaf debris, and frass (excrement).

During the larval stage one 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 back. 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.

Mid-July through early August is the gypsy moth pupa 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. After about 10 days of metamorphosis the adult winged moth emerges, leaving the pupa cases behind. Female pupa are larger than male pupa.

Gypsy moths spend August through September mating and laying eggs. 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.
(Courtesy of the Roscommon County Gypsy Moth Program.)

Posted by sovazone sovazone, June 21, 2020 18:11


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