ASPECTS OF THE COURTSHIP BEHAVIOR OF THE BLACK WIDOW SPIDER, LA TRODECTUS HESPER US (ARANEAE: THERIDIIDAE), WITH EVIDENCE FOR THE EXISTENCE OF A CONTACT SEX PHEROMONE

The courtship and mating behavior of the black widow spider, Latrodectus hesperus Chamberlin and Ivie, were studied to determine stimuli responsible for mate location and courtship initiation in this species. We observed new courtship patterns which included a vigorous display performed by females, "push-ups" executed by both sexes, and cryptic abdominal vibrations produced by males immediately upon contact with female webs. Males initiated courtship when they contacted unoccupied conspecific female webs, but did not respond when placed on other male webs. Male L. hesperus also initiated courtship behavior on unoccupied female webs of another species, Latrodectus mactans (Fabricius). Female L. hesperus were stimulated by contact with conspecific male webs, but not other female webs. Scanning electron microscopy revealed what are presumed to be chemoreceptive hairs on the tarsi and pedipalps of males and females. We conclude that male and female L. hesperus produce sexually specific, complementary contact pheromones which are incorporated into their silk. These substances apparently function in mate location, sex identification, and courtship for this species, but not as an isolating mechanism between L. hesperus and L. mactans.