Nuptial feeding by male bushcrickets: an indicator of male quality

Male bushcrickets transfer a spermatophore at mating that consists of a sperm-containing ampulla and a product of the accessory glands, the spermatophylax, that is consumed by the female during insemination. Male Requena vaticalis produce functionally different spermatophores depending on the availability of sexually receptive females. They will maintain high mating frequency by providing a gift sufficient to ensure sperm transfer, or will invest parentally in females when their mating frequency is low. We examined the relationship between male quality and nuptial feeding under conditions where males invest in ejaculate protection or in parental investment. When investing in ejaculate protection, males reduced the quality of the spermatophylax meal by I educing both the concentration of protein and the absolute amount of protein it contained. There was no relationship between male phenotype and gift size or quality. Moreover, we could find no evidence for the recently advanced hypothesis that females can exercise mate choice by interfering with insemination. However, when males were investing parentally, we found a positive association between spermatophylax size and male size, but no relationship between protein content and male size. Males with high levels of fluctuating asymmetry invested more heavily in the nutritional content of their spermatophylaxes than did symmetrical males. Thus, male quality does influence nuptial feeding, but in a manner predicted by a model of indirect fitness benefits from mate choice.