HESSIAN FLY (Phytophaga destructor), a small fly native to Europe, extremely destructive to wheat crops, especially in the United States and Canada. It is dark in colour, resembling a mosquito. Its larvae, which are greenish white, attack the stems of wheat, barley and rye. There are two generations annually in most parts of the United States, but only one generation in the more northern States and Canada. The wheat crop especially is frequently damaged by the Hessian fly to an amount which has been estimated at from ten to twenty millions of dollars. The general method of control is to sow wheat late enough to escape the fly. All volunteer wheat plants should be destroyed. The popular name is derived from the fact that the insect is supposed to have been introduced into the United States in straw bedding used for the Hessian troops during the Revolutionary War. (See DIPTERA ; ENTOMOLOGY.)