Behaviour 2019
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Risky business: Males choose more receptive adults over safer subadults in a cannibalistic spider
Lenka Sentenská1,2, Catherine Scott1, Pierick Mouginot3, Maydianne Andrade1. 1University of Toronto Scarborough, Toronto, Ontario, Canada; 2University of Greifswald, Greifswald, N/A, Germany; 3Université de Perpignan, Perpignan, N/A, France

Male brown widow spiders (Latrodectus geometricus) can mate with adult as well as immature (subadult) females. Mating with adults starts with lengthy courtship and ends with female cannibalistic attack, but mating with subadults involves only brief courtship and no cannibalism. Therefore, male preference of subadult over adult females is predicted. We investigated male mate choice, and despite our expectations, males chose contact pheromones of adults. This suggests either that males do prefer adult females or that subadult females produce weaker or no chemical signal. We swapped adult and subadult females between webs, and show that some courtship components are triggered solely by contact with the silk (web alteration) or body (silk binding) of adult females, but vibratory courtship occurs regardless of the web origin or developmental stage. In our experiments, subadults females were more reluctant to mate than adults. We conclude that males can detect subadult females, but are more likely to invest in mating attempts with adults. Low courtship investment may explain the reduced receptivity of subadults, or could be an evolutionary response of males to lower subadult receptivity.