Size-biased Mating in Both Sexes of the Black-horned Tree Cricket, Oecanthus nigricornis Walker (Orthoptera: Gryllidae: Oecanthinae)

Abstract

Previous studies on tree crickets have demonstrated female choice of males based on size and courtship feeding but less is known about sexual selection under conditions of direct mating competition. I studied courtship, aggression and mating of the black-horned tree cricket Oecanthus nigricornis (Walker) to test size-related sexual selection under conditions of direct sexual competition. Results show that larger individuals of both sexes mated more frequently than their smaller counterparts, and this was due to the ability of large individuals to out compete rivals. Large males achieved the advantage by aggressively reducing courtship by small males, whereas large females responded to male courtship more quickly but with little aggression. Although there was no evidence here for mate choice, there were advantages for having larger mates; fecundity increased with female size and spermatophores (which females consume after mating) increased with male size. Size of the specialized metanotal courtship gift, however, was not related to male size.