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

Spiders are exemplary loners: most species are solitary, territorial, and e ven cannibalistic throughout much of their life spans. Communication betwee n individual spiders involves agonistic signalling in the form of vibratory and visual displays, which serves to maintain a widely dispersed populatio n. 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 aper ta, and used the synthetic compounds to test conclusions reached from previ ous behavioural trials indicating that chemical cues emitted by this female class attract courting males. We also investigated the role of chemical co mmunication 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 beha viour from them at very low dosages. Pheromonal cues release most elements and stages of the male courtship sequence in A. aperta. Two fundamental dif ferences were observed, however, between the courtship males displayed in t he presence of pheromone alone versus in the presence of a sexually recepti ve female. (1) Behaviour patterns associated with locating a female were si gnificantly more frequent in the pheromone-alone treatment sequences. (2) M ale actions, such as wave legs, lunge and retreat, were observed only in th e female-present trials. These latter acts were displayed in response to fe male actions made towards the courting male. (C) 2001 The Association for t he Study of Animal Behaviour.