“…The assumption underlying this analysis is that the continuous nature of the trait is phenotypically evident. But many traits occur as discrete, rather than continuously distributed, characters: for example, dimorphic variation in morphological structures in cladocera (Dodson,1 989), beetles and earwigs (Eberhard & Gutiérrez, 1991); thrips (Crespi, 1988), Hymenoptera (Danforth, 1991;Elmes, 1991); paedomorphosis in amphibia (Harris et a!., 1990); wing dimorphism in insects (Roff, 1986a); mating behaviour (see Table 7.7 in Roff, 1992); sex ratio (Bull et a!., 1982) and diapause . Although these traits appear phenotypically discrete, their inheritance may be polygenic, the particular manifestation of the trait being a function of a threshold of sensitivity.…”