The gypsy moth is now one of the most challenging insect pest species in north america. with hundreds of known plant hosts, many of which are completely defoliated during outbreak years, the gypsy moth has no shortage of food and defoliation lasting two or more years can cause significant tree mortality. today this introduced species is considered an invasive species. the gypsy moth became established in the u. s. for all but one of the following reasons. a) female gypsy moth egg masses may contain over 1,000 eggs. b) females cannot fly so it may take longer for the species to reach surrounding areas and flourish. c) the caterpillars that hatch from eggs are capable of feeding on over 300 species of trees and shrubs. d) predators, parasitoids, and diseases that would feed on the egg masses in its native habitat are not present.