The gypsy moth was brought to North America in 1869 by Mr. L. Trouvelot in a misguided attempt to breed a hardy silkworm. Some escaped and the first recorded defoliation by gypsy moth was in 1889 of the street trees in Trouvelot's own neighborhood of Medford, Massachusetts.

Lacking many natural enemies, the gypsy moth has escalated into the most important insect pest of forest and shade trees in the eastern United States. They have moved steadily westward ever since, reaching Wisconsin in the late 1980s.

The gypsy moth is native to Europe, Asia, and North Africa. It has succeeded so well in North America for several reasons:

• This species is very hardy. In its native range gypsy moths can be found from the frigid Russian steppes to the subtropical shores of the Mediterranean.
• The gypsy moth is not fussy about what it eats; it has been recorded feeding on over 600 species of trees and shrubs.
• Finally, when the gypsy moth was introduced into North America, none of the natural enemies that preyed upon it in its native range were present. Pest managers have since introduced some of the parasites and diseases that suppress gypsy moth populations in Europe and Asia, but only about a dozen are well established in North America.