An airborne female pheromone associated with male attraction and courtship in a desert spider

Abstract

Spiders are exemplary loners: most species are solitary, territorial, and even cannibalistic throughout much of their life spans. Communication between individual spiders involves agonistic signalling in the form of vibratory and visual displays, which serves to maintain a widely dispersed population. Pheromones, however, have been implicated in bringing the sexes together during reproduction. We identified two potential sex pheromones collected from virgin, sexually mature females of the desert spider, Agelenopsis aperta, and used the synthetic compounds to test conclusions reached from previous behavioural trials indicating that chemical cues emitted by this female class attract courting males. We also investigated the role of chemical communication in prescribing the complex male courtship sequence. In separate trials, one of the synthesized pheromones, 8-methyl-2-nonanone, was found both to attract males to the source of the cue and to elicit courtship behaviour from them at very low dosages. Pheromonal cues release most elements and stages of the male courtship sequence inA.aperta . Two fundamental differences were observed, however, between the courtship males displayed in the presence of pheromone alone versus in the presence of a sexually receptive female. (1) Behaviour patterns associated with locating a female were significantly more frequent in the pheromone-alone treatment sequences. (2) Male actions, such as wave legs, lunge and retreat, were observed only in the female-present trials. These latter acts were displayed in response to female actions made towards the courting male.