Flight polymorphism in the field cricket Gryllus pennsylvanicus.

Wing length polymorphisms are common in many groups of insects. In the field cricket Gryllus pennsylvanicus the long-winged morph occurs in low frequency in most populations but seems not to occur at all in certain areas and to become relatively abundant in others. Laboratory rearing experiments and single-pair crosses suggest that both inter-and intrapopulation variation can be explained at least in part by genetic differences. A model of genetic variation in threshold response is consistent with all available data. One possible mechanism for maintenance of the flight polymorphism is discussed.