Web reduction behaviour and the chemical communication system of the western black widow, Latrodectus hesperus

In spiders, pheromones mediate intersexual attraction, courtship behaviour, and mate recognition. I studied the chemical communication system of the western black widow spider, Latrodectus hesperus. Females attract males to their webs with silk-borne sex pheromones. Contact with the silk elicits courtship behaviour by males. Often, the courting male engages in web reduction behaviour, during which he excises and bundles up sections of the web and wraps them with his own silk. Using analytical chemistry, and behavioural tests in both the laboratory and the field, I investigated (1) the molecular structure and function of the female’s contact sex pheromone, and (2) the function of web reduction behaviour. A silk-borne contact pheromone elicits web reduction behaviour, and a serine derivative similar to the pheromone of congeneric L. hasselti is one constituent of the multi-component pheromone. Web reduction decreases web attractiveness to rival males in the field, thereby limiting male-male competition.