Reproductive Behaviour of the Decorated Cricket, Gryllodes Supplicans (Orthoptera: Gryllidae): Calling Schedules, Spatial Distribution, and Mating

Abstract

The temporal and spatial patterns of sexual activity in the cricket, Gryllodes supplicans, were examined. Calling by males in a natural population occurred throughout the night, reflecting the temporal availability of females. In an outdoor enclosure, females were significantly more likely than males to change locations from one hr to the next; the average probability of such a change by a female was 0.6, and this did not vary significantly over the course of a night. The locomotor activity of females, as indicated by the average distance an individual moved each hour (and between nights), also was significantly greater than that of males. The greater mobility of females increased their access to additional males, and probably allowed them to consume more spermatophores (sperm-containing vessels transferred by males which remain outside females' bodies after mating) than they would otherwise obtain by remaining with the same mate. An increased demand by females for additional spermatophores was evidenced in the laboratory by repeated mating, frequent consumption of spermatophores, brief intercopulatory intervals, and the theft of spermatophores from mated females. Spermatophore theft demonstrates that females solicit spermatophores for benefits other than genes (i.e. nutrition), and has not previously been reported for any insect. In contrast to females, males exhibited increased site fidelity and reduced locomotor activity in the enclosure. By calling only when hidden and stationary, males probably reduce the possibility of detection by acoustically orienting predators. Males also occurred beneath shelters with other calling males, but did not themselves call or did so at reduced levels. These males probably were 'satellites', silent males that locate next to calling males and intercept the phonotactically responding females.