Copula duration and sperm storage in Mediterranean fruit flies from a wildpopulation

In the Mediterranean fruit fly (Ceratitis capitata Weidemann, 'medfly'), a lekking tephritid, evidence from laboratory studies of flies from laborator y strains suggests that copulation is shorter, and sperm storage more abund ant, if males are large or protein-fed, and that copulation is longer when females are large. In addition, sperm tend to be stored asymmetrically betw een the female's two spermathecae and this asymmetry declines with abundanc e of stored sperm. The primary objective of this study was to investigate w hether these trends persist in other experimental contexts that bear closer resemblance to nature. Accordingly, we carried out experiments in a field- cage using males derived as adults from a wild population and virgin female s reared from naturally infested fruit. The results of this study were cons istent with laboratory studies in that copula duration increased with femal e size, that sperm were stored asymmetrically between the females' spermath ecae, and that this asymmetry declined with number of sperm stored. However , we also found some previously unreported effects of female size; large fe males stored more sperm and stored sperm more asymmetrically between their two spermathecae than did small females. Unlike the laboratory studies, cop ula duration and sperm storage patterns were unaffected by male size and di et. This may be due to overwhelming variation from other sources in the wil d-collected males used, as well as environmental variability in the semi-na tural setting.