Optimal Clutch Size for Maximizing Reproductive Success in a Parasitoid Fly, Exorista japonica (Diptera: Tachinidae)

Abstract

The number of adults emerging from a host, their size in terms of puparium weight, mortality and sex ratio of Exorista japonica were examined in relation to clutch size per larva of the host, Pseudaletia separata. Effects of female size on fecundity and longevity were also examined. The mean number of adults emerging from the host increased as clutch size increased up to 15. Body size, however, decreased markedly with increasing clutch size. Sex ratio was not significantly different from 0.5. Survival ratio of eggs to adults correlated negatively with clutch size. There was a positive correlation between the size of females and their fecundity, but no correlation between size and longevity. The relationship between clutch size and total number of eggs expected from female offspring was also examined. Reproductive success gained from one egg was maximized when clutch size was 1, while that gained from one host attained its maximum when clutch size was 10.