Wing polymorphism in Pyrrhocoris apterus (Heteroptera, Pyrrhocoridae): penetrance of recessive macropterous homozygotes and duration of larval development

Abstract

The length of egg-to-adult development was compared in two strains of P. apterus selected for brachyptery or macroptery. Selection influenced the frequency of the receissive allele for macropterism (q), the penetrance of recessive homozygotes (P), and the average duration of development. In branchypters, average length of development was not affected by q, but was positively correlated with P (r = 0.889 in males and 0.941 in females). The anova revealed that 74.4% of variance of P was due to genetic, and 16.5% to photoperiodic factors. Development duration of macropters (being greater than in brachypters) was not correlated with P or q. We suppose that some phenotypic brachypters begin to develop as potential macropters, are diverted to brachypter development in the late larval stage, and therefore have longer larval development than “ordinary” brachypters. As the ratio of “brachypterized” to “ordinary” brachypters increases with P, the average duration of development of all phenotypic brachypters increases also with P. In some populations short development may have adaptive significance. The linkage between P and length of larval development may contribute to geographic differentiation of the tendency to produce (non-functional flightless) macropters.