Life-history theory predicts trade-offs between resources invested in reproduction and other fitness-related traits. To date, most studies have focused on potential reproductive trade-offs in females. However, it is now generally accepted that reproduction is also costly for males, and thus males too may be subject to trade-offs. We examined the relationship between development time and the production of both fertile and non-fertile sperm in males of the African bush brown butterfly (Bicyclus anynana) selected for short or long pre-adult development time. Fast developing males ejaculated fewer non-fertile sperm on their first mating, suggesting that there could be a trade-off between ejaculate production and development time in this species. Contrary to predictions, slow developing males were smaller, produced fewer fertile sperm and took longer to mate. We discuss why this might be the case, and suggest that there may be a cost to the production of non-fertile sperm in the Lepidoptera.
We examined whether dispersal was associated with body and wing morphology and individual quality, and whether such an association was sex-specific, in the Glanville fritillary butterfly Melitaea cinxia (L.) in Paldiski on the north coast of Estonia. Body weight, size and shape of both fore- and hindwing, wing aspect ratio and wing loading were used as measures of body and wing morphology. Fluctuating asymmetry (FA) of wing shape was used as a measure of individual quality. Males and females did not differ in dispersal rates, despite large differences in overall morphology and FA. Females had a significantly higher wing loading and aspect ratio, but a lower FA than males. Females, but not males, that dispersed differed in forewing shape from those that did not disperse. The sex-specifity of the covariation between dispersal and forewing shape is most probably due to wing shape being associated with different life-history traits in both sexes, resulting in different selection pressures on wing shape in each of the sexes.