Behaviour 2019
Intrasexual conflict - female false widow spiders respond and adapt to conspecific female sex pheromone
Andreas Fischer, Sula Fernando, Sarah Moniz de Sa, Jamie-L Varney, Regine Gries, Gerhard Gries. Simon Fraser University, Burnaby, BC, Canada

Studies on intrasexual conflict focused on the mate-seeking sex, with little attention paid to the signalling sex. Females of cob-web spiders, such as the false black widow Steatoda grossa, can alter the architecture of their webs in relation to external cues to upturn prey-capture, safety, or mating opportunities. Here, we tested the hypothesis that female S. grossa respond to mate competition in that they change the web-architecture and pheromone amount on it, in response to the number density of webs in a microhabitat. In experiment 1, three females (low-number density) built their webs in the same room for two days. Following a 12-day intermission, the same three females then built a new web for two days, together with 27 other females (high-number density) present in the same room. The design of experiment 2 was similar except that females first built their webs in the high-number density setting and then in the low-number density setting. The females’ web architecture and pheromone titer in both density settings were measured. Our data support the hypothesis that females adapt web architecture and pheromone amount, in response to the number density of webs in a microhabitat