BugInfo Gypsy Moths

ORDER: Lepidoptera | GENUS: Porthetria | FAMILY: Lymantriidae | SPECIES: dispar

History of Gypsy Moths in the U.S. Along with other species, the Gypsy Moth was imported into the United States in the mid-nineteenth century with the intent of finding a species of silk producing moth that could be hybridized to compete favorably with the Silkworm Moth, yet not be subject to the many diseases that the Silkworm Moth suffered in cultures. This experiment was conducted by Leopold Trouvelot, an amateur lepidopterist from Medford, Massachusetts, who at one time had more than a million larvae in cultivation behind his house. In 1868 or 1869, several individuals of adult Gypsy Moths escaped from his house, with ten years elapsing before the neighborhood trees were badly defoliated by resulting populations of the moth. From that start, Gypsy Moths have become one of the most important forest pests in the United States, defoliating millions of acres in the northeastern U.S. The Gypsy Moth continues its spread, extending into Virginia, North Carolina and Michigan, with isolated pockets in the Pacific Coast states.

Distribution method. The Gypsy Moth has special methods of dispersal. The young larvae have hairs with small air pockets that create buoyancy, allowing them to travel great distances when the wind is strong. They have been found as high as 2,000 feet in the air, and are known to travel five miles a day by this method. Adult females commonly pupate and deposit egg masses on motor vehicles, especially trucks and recreational vehicles that are parked near or under trees.

Life History: Females lay eggs on the trunks of trees, each egg mass including several hundred eggs. Gypsy Moths overwinter in the egg stage, and hatch in April or May. The young caterpillars are black and hairy, later becoming mottled gray with tufts of bristlelike hairs, and blue and red spots on the back. There is one generation per year. Gypsy Moths have preference for oaks, but they will attack the foliage of most trees and shrubs. Adults differ in appearance, males being brown with a fine, darker brown pattern on the wings. Females are nearly white, with a few dark markings on the wings. Females do not fly. Caterpillars climb trees and feed mostly at night. They are capable of denuding foliage from trees, and this activity will kill many trees if repeated over a few years. Trees also become weakened and more susceptible to diseases and wood boring insects.

Control of Gypsy Moths. Egg masses can be scraped from trees and burned. Sticky bands may be placed around trees to prevent the larvae from climbing to the foliage. After World War II, DDT was used for chemical control and was very effective. However, many other animals from Honeybees to bald eagles were killed or affected also. Nearly 50 species of insects that are parasitic on Gypsy Moths have been introduced for biological control, and this strategy has undoubtedly prevented the Gypsy Moth from becoming even more destructive. Bacterial, fungal, and viral diseases are other likely control agents, currently being explored as possibilities in integrated pest management for the Gypsy Moth.


Selected References:

Doane, C. C. and McManus, M. L., editors. 1981. The Gypsy Moth: Research toward Integrated Pest Management. U. S. Department of Agiculture Forest Service Science and Education Agency, Technical Bulletin 1584.

Forbush, E. H. and Fernald, C. H. 1896. The Gypsy Moth. Wright & Potter, Boston.

Gerardi, M. H. and Grimm. J. K. 1979. The History, Biology, Damage, and Control of the Gypsy Moth, Porthetria dispar (L.). Associated University Presses, Cranberry, New Jersey.

Leonard, David E. 1974. Recent developments in the ecology and control of the Gypsy Moth. Annual Review of Entomology, Volume 19.


Prepared by the Department of Systematic Biology, Entomology Section,
National Museum of Natural History, in cooperation with Public Inquiry Services, 
Smithsonian Institution

Information Sheet Number 36, 1996