Morag, N., Department of Life Sciences, Ben-Gurion University, Be'er Sheva, Israel
Keasar, T., Department of Biology, University of Haifa, Tivon, Israel
Harari, A., Department of Entomology, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
Bouskila, A., Department of Life Sciences, Ben-Gurion University, Be'er Sheva, Israel

Maternal pre-reproductive experience can impose phenotypic changes on offspring traits. These modifications may result from physiological constraints, although they can also increase the adaptation of offspring to their anticipated environment. Distinguishing between the two interpretations is often difficult. The effects of virgin female rearing density on their longevity and the characteristics of their male offspring are explored in the polyembryonic parasitoid wasp Copidosoma koehleri (Blanchard) (Encyrtidae: Hymenoptera). High rearing density may adversely affect maternal physiology or, alternatively, act as a cue for anticipated competition during the lives of the mothers and their offspring. Male offspring of group-reared females reach pupation significantly sooner than male offspring of females reared alone. This accelerated development may provide an advantage when competition from superparasitising individuals is expected. The lifespan of high-density females is longer than that of singly-reared females, and their male offspring survive longer, suggesting that crowded rearing does not reduce the fitness of females or offspring. The shortened development time of male offspring may reflect an adaptive epigenetic response to predicted competitive conditions. © 2011 The Authors. Physiological Entomology © 2011 The Royal Entomological Society.