6 - The evolution of edible ‘sperm sacs’ and other forms of courtship feeding in crickets, katydids and their kin (Orthoptera: Ensifera)

Summary

ABSTRACT

Males of certain arthropods feed their mates during mating. Nowhere is the diversity of this courtship feeding greater than in the Orthopteran suborder Ensifera, the katydids, weta, and the humped–winged, wood, Jerusalem, mole, cave, camel as well as tree and other true crickets. In this chapter I discuss the origin and current utility of male glandular and body–part donations in the Ensifera. Character analysis shows that the ancestral ensiferan female removed and ate a sperm ampulla (spermatophore) that was positioned externally on her genitalia. This was followed by at least 11 origins of mate feeding, most cases of which involved female feeding on the male contribution during insemination. This sequence of events indicates that male contributions evolved through sexual selection and sexual conflict as meal size increased and prolonged the attachment of the sperm ampulla, thus increasing paternity. The most common type of male contribution in Ensifera – a gelatinous spermatophylax attachment to the sperm ampulla – evolved three times. A spermatophylax is found in virtually all katydid species (Tettigoniidae) and the other four families in the same clade. For the current utility of courtship feeding there is experimental support for different functions in different species: in a humpedwinged cricket (Haglidae), two true crickets (Gryllidae) and two katydids, wing, gland or spermatophylax feeding increases paternity by preventing consumption of the sperm–ampulla. In cases of precopulatory feeding, the meal functions to obtain mates.