Courtship Feeding in Katydids (Orthoptera: Tettigoniidae): Investment in Offspring or in Obtaining Fertilizations?

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Abstract
Studies indicate that courtship feeding in insects represents mating effort that evolved to ensure successful insemination. I tested this hypothesis with katydids (Requena verticalis), in which males feed females after mating by producing a sperm-free mass, the spermatophylax, from reproductive accessory glands. Although courtship feeding in this species prevents the female''s removing and eating the sperm-containing ampulla before insemination has occurred, the spermatophylax is more than twice the size necessary to transfer a full complement of sperm and to transfer substances preventing female response to male sexual sounds. Thus, I reject the hypothesis that the function of "excess" male-donated nutrition is mating effort that protects the ejaculate. The size of the spermatophylax probably did not evolve only as a result of intersexual selection by premating female choice for males capable of producing larger contributions. Since feeding on spermatophylax nutrients by females increases egg size, and possibly offspring fitness, courtship feeding in R. verticalis may represent parental effort whereby males invest in their own zygotes.