Maternal effects and their consequences for offspring fitness in the Yellow Dung Fly

1. Maternal adult diet and body size influence the fecundity of a female an d possibly the quality and the performance of her offspring via egg size or egg quality. In laboratory experiments, negative effects in the offspring generation have often been obscured by optimal. rearing conditions. 2. To estimate these effects in the Yellow Dung Fly, Scathophaga stercorari a, how maternal body size and adult nutritional status affected her fecundi ty, longevity and egg size were first investigated. 3, Second, it was investigated how female age and adult nutritional experie nce, mediated through the effects of egg size or egg quality, influenced th e performance of offspring at different larval densities. 4. Maternal size was less important than maternal adult feeding in increasi ng reproductive output. Without food restriction, large females had larger clutch sizes and higher oviposition rates, whereas under food restriction t his advantage was reversed in favour of small females. 5. Offspring from mothers reared under nutritional stress experienced reduc ed fitness in terms of egg mortality and survival to adult emergence. If th e offspring from low-quality eggs survived, the transmitted maternal food d eficiency only affected adult male body size under stressful larval environ ments. 6. Smaller egg sizes due to maternal age only slightly affected the perform ance of the offspring under all larval conditions.