Courtship feeding increases female reproductive success in bushcrickets

Abstract

Parental investment theory suggests that investment by males through courtship feeding of their mates may represent an important source of nutrition which increases female fitness and ultimately influences patterns of sexual selection^1,2. In certain insects males provide nutritional products from reproductive accessory glands during mating; these are either eaten by the female or are absorbed in her genital tract^2,3. Male bushcrickets (Orthoptera: Tettigoniidae) feed their mates with an elaborate spermatophore consisting of a spermatophylax, which is eaten by the female after mating, and a sperm ampulla, eaten after the ejaculate has emptied^4,5. Studies of bushcricket mating systems have indicated that spermatophore nutrients are important to females—females prefer to mate with males able to supply larger spermatophores⁶—and field studies of species with very large spermatophores have revealed a role-reversal in reproductive behaviour, with females aggressively competing for males capable of producing spermatophores^7,8. Although radiolabelling experiments (with several insect species) have demonstrated that male-derived nutrients are incorporated into eggs^3,9–11, these studies do not demonstrate that this sort of courtship feeding enhances female fitness. Here I report the results of an experiment which shows that feeding on the spermatophore enhances the reproductive success of female bushcrickets (Requena verticalis Walker) by increasing the numbers and size of eggs produced.