Energy beyond the pupal stage: larval nutrition and its long-time consequences for male mating performance in a scorpionfly

The basic requirement for selection to take effect is variation in fitness relevant traits among individuals of a population. This study is concerned with the question whether environmental conditions met during an early phase of life history that is dominated by the natural component of selection will affect traits and behaviour in a sexual selection context after metamorphosis in a holometabolous insect species. We examined the effects of nutrition as a proximate factor responsible for intrasexual phenotypic variation in the mating performance of male Panorpa vulgaris (Mecoptera: Panorpidae). For this purpose, we manipulated food availability during larval development as well as during adulthood. To obtain matings and to increase their reproductive success males must secrete salivary masses which are then consumed by the females during copulation. The results of the present study are consistent with those of previous studies demonstrating a strong effect of nutrition during adulthood on various fitness relevant traits (salivary gland development, saliva investment in copulations, etc.). But moreover, we could show that food availability during larval development affected male body weight and that there was an interaction between larval and adult diet affecting salivary gland weight relative to body weight. Therefore, food availability during the larval stage can become an important and limiting factor for salivary gland development (and mating success) depending on food availability during adulthood. Several other variables (number of salivary masses, copulation duration, salivary mass weight and saliva investment) seemed not to be associated with larval nutrition.