The hessian fly or barley midge, Mayetiola destructor, is a species of fly that is a significant pest of cereal crops including wheat, barley and rye. Though a native of Asia it was transported into Europe and later into North America, supposedly in the straw bedding of Hessian troops during the American Revolution (1775–83). There are usually two generations a year but may be up to five. In the spring the dark-coloured female lays about 250 to 300 reddish eggs on plants, usually where the stems are covered by leaves; the larvae feed on the sap and weaken the plants so that they cannot bear grain. The hessian fly was described by Thomas Say in 1817.