Mating and cannibalism dynamics of the fishing spider Dolomedes scriptus Hentz, 1845 (Araneae: Pisauridae)

Abstract. Sexual cannibalism is common in many species of arachnids. Studies investigating Dolomedes tenebrosus Hentz, 1844, have even discovered the occurrence of obligatory male self-sacrifice during copulation. In this system, females subsequently cannibalize males, and this cannibalism leads to higher fitness for both partners. Unfortunately, our understanding of the evolution of such an extreme mating system is challenged by the absence of information for close relatives. To that end, this study explores the courtship behavior, mating system and cannibalism dynamics of the spider Dolomedes scriptus Hentz, 1845. To determine whether female and male D. scriptus mate multiply, we recorded interactions of repeatedly exposed focal females and focal males to new mating partners for three days. We also quantified attacks and cannibalism events that occurred both before and after every copulation. We found male D. scriptus court females by waving their forelegs during their approach and tapping the females prior to mounting. In our remating trials, none of the female D. scriptus accepted additional males after their first mating over the three-day period. In contrast, male D. scriptus were polygynous, often mating with multiple females. Across the trials, sexual size dimorphism was a predictor of whether mating occurred, with similarly sized pairs being more likely to mate. Additionally, previously mated females were less likely to cannibalize males—an unusual pattern for spiders. Like other species of Dolomedes Latreille, 1804, our results suggest a strong role of female aggression in D. scriptus mating system dynamics.