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AbstractIn this study, survival to adult stage, duration of development of the immature stages, egg micromorphology, DNA polymorphism, and reproductive compatibility were measured for early- and late-emerging phenotypes of Delia radicumLinneaus to determine whether both phenotypes had evolved differences other than the duration of puparial development and to find the most likely genetic system controlling the expression of both phenotypes. Survival to adult stage was not significantly different between the early- and late-emerging phenotypes. Random amplified polymorphic DNA (RAPD) primers tested suggest that it is possible to distinguish an early-emerging fly from a late-emerging fly. Furthermore, the results suggest that the early- and late-emerging phenotypes differ not only in the timing of adult emergence but also in their egg structure (egg micromorphology) and in their larval and puparial mortality. These two phenotypes are not reproductively or ecologically isolated. The genetic system controlling the expression of early and late emergers in a population of D. radicumis probably an adaptive strategy reducing predator and parasitoid pressures, optimizing resource utilization, and ensuring survival of D. radicumduring atypical winters. This strategy could eventually lead to temporal sympatric speciation if there are changes in a few key loci responsible for host plant selection and fitness on a new host.

AbstractNo sexual dimorphism in weight was observed at emergence of adult Aleochara bilineataGyll. (Coleoptera: Staphylinidae). The weight of adults was strongly correlated with the size of the pupa in which the parasitoid developed. Newly emerged adults increased in weight after feeding, and this increase was greater in females than in males, reflecting the beginning of oogenesis. We showed that females invested simultaneously in reproduction and somatic functions the first day following mating. Although males and females showed no significant differences in weight at emergence, the females fed actively upon emergence and weighed significantly more than the males for 30 days after emergence. After that period, most of the eggs has been laid and both male and female weights were similar.