Strategic male mating effort and cryptic male choice in a scorpionfly

In animal species with high male mating effort, males often find themselves in a dilemma: by increasing their mating effort, the gain from each copula tion increases but simultaneously reduces available resources and, thus, th e opportunity for future copulations. Therefore, we expect males to spend l ess reproductive resources on matings that provide low reproductive potenti al, thereby saving resources for future copulations, possibly with high-qua lity females, a sort of cryptic male choice. However, the strength of the t rade-off between nvestment in a current mating and resources available for future matings must not be the same for all males. Males with relatively hi gh mating costs should allocate their limited resources more cautiously tha n males with more plentiful resources. Here, we examine this prediction in the scorpionfly Panorpa cognata. Prior to copulation, males produce a large salivary mass on which females feed during copulation. We show that the pr oduction of larger salivary masses leads to longer copulations. Moreover, t he size of the salivary gland and salivary mass increases with increasing m ale condition. However, males in poor condition make a relatively higher ma ting investment than males in good condition. We therefore expect male cond ition to influence cryptic male choice. In accordance with our hypothesis, only males in poor condition choose cryptically, producing larger salivary masses in copulations with females of high fecundity.