Line-following preferences of male crab spiders, Misumena vatia

Male crab spiders locate cryptic females by methods that have proved elusive to researchers. Previous work has suggested that female draglines provide males with clues to the presence of females. Unlike other wandering spiders, however, M. vatia do not deposit mate-attracting pheromones on their draglines. Based on evidence that the size and strength of draglines vary predictably with the age and sex of the source spider, we tested the hypothesis that mechanical cues allow males to identify the age, sex and species of the dragline producer. We ran adult and penultimate male crab spiders through a series of trials to identify preferences for following different types of dragline. A spider's developmental stage influenced its response to draglines of other individuals, suggesting that these responses were influenced by the search for mates. Adult males preferred adult and juvenile female draglines and selected conspecific adult female draglines over draglines from adult females of a related species. Penultimate males did not show significant preferences in these tests. Mechanical cues may therefore moderate the responses of the adult males to foreign draglines. We consider dragline following in M. vatia as a model of how cues produced in a nonmating context may facilitate mate search, and we suggest that study of such species-specific environmental modifications may shed insight into the evolution of mate location systems.