Abstract
Wing polymorphism commonly occurs in many insects, especially species of Orthoptera, Coleoptera, Homoptera, and Hemiptera (Harri-son, 1980). The polymorphism consists of dis-crete differences in wing length with morphs exhibiting fully developed, reduced, or to-tally absent wings. In addition to differences in wing length, morphs often differ in a number of other characteristics such as degree of fl ight muscle development, duration of nymphal de-velopment, time to fi rst reproduction, fertility and diapause (Anderson, 1973; Vepsalainen, 1978; Harrison, 1980). Wing polymorphism is an attractive sys-tem for investigating the evolution of disper-sal in natural populations (Vepsalainen, 1978; Denno and Grissell, 1979; Harrison, 1980). A key step in such studies is the identifi cation of the environmental and genetic components of morph determination. Numerous studies of insects from several different orders have clearly demonstrated that environmental vari-ables such as photoperiod, temperature and density may strongly infl uence the develop-ment of an individual into a particular morph (see references in Harrison, 1980). However, the genetic component of morph determina-tion is poorly understood. In a number of studies, attempts have been made to identify the genetic basis of determi-nation in species of waterstriders (Gerridae: Hemiptera), and the results used to formulate models of the evolution of winglessness. Pois-son (1924) claimed that results of crossing ex-periments with
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