Amanda Johnson & Orenda Revis

            Chemical prey cues influence the urban                microhabitat preferences of black widow spiders

Animals are known to utilize chemical cues in a number of functional contexts.   For example, pheromonal cues have been clearly shown to shape many animal mating systems.  In addition,  the study of predator-prey dynamics is being revolutionized as we learn more about the capabilities of animals to use chemical information to avoid predators and/or locate prey.  Such chemicals that allow one organism to exploit another are referred to as kairomones.  Spiders offer a good model system for the study of kairomones as they are known to be important predators in terrestrial ecosystems, and several species have been shown to use chemical cues to avoid predators and/or locate prey.  However, the extent to which chemical prey cues actually drive habitat use by many spider taxa remains unclear.  Black widow spiders (Latrodectus spp.) are both a species of medical importance owing to the danger their venom presents to human victims, and a common urban, agricultural and invasive pest.  In this study we used the Western black widow, Latrodectus hesperus, to test the hypothesis that spiders are capable of detecting chemical cues left by potential prey items and adjust their habitat preferences (i.e. web building behavior) accordingly.  Our results showed a significant preference by black widows to build their webs in areas that contain chemical prey cues. We discuss the implications of this finding for our understanding of urban black widow habitat use, population dynamics and the potential for urban infestations.