Spermatophore size and its role in the reproductive behaviour of the cricket, Gryllodes supplicans (Orthoptera: Gryllidae)

Abstract

The spermatophore that a male cricket of Gryllodes supplicans transfers to the female during mating, includes a large gelatinous portion (spermatophylax) that is removed and consumed by the female after mating. In other North American cricket species, the spermatophore consists solely of a small sperm-containing ampulla. In this study, the role of spermatophore size in the reproductive behaviour of G. supplicans was examined, along with the costs associated with the provision of a more complex spermatophore. The mean intercopulatory interval of male G. supplicans that were allowed constant access to receptive females was 3.25 h; this period is long relative to those of other crickets. The estimated weight of spermatophores produced by males did not differ significantly from that of spermatophores produced by these same males 24 h later; males apparently hold constant their investment in subsequent copulations. The time taken by females to consume the spermatophylax fully increased linearly with the weight of the spermatophore. Females remove the sperm ampulla soon after consuming the spermatophylax and thus penalize males that provide smaller "nuptial meals." Larger males produce heavier spermatophores; thus, small males often may be at a selective disadvantage. These results, when examined in the light of the ampulla-removal behaviour of females, suggests that females are capable of adaptive mate choice.