Sexual cannibalism is an extreme form of sexual conflict that may have broad evolutionary effects on mating behaviour. Latrodectus spiders (∼30 “widow” species) could enable comparative tests of the evolution of sexual cannibalism, but most species are poorly-studied. Here we describe the mating and remating behaviour of a species endemic to South America, L. mirabilis, with a focus on the occurrence and consequences of sexual cannibalism. Mating and cannibalistic behaviours were novel relative to other Latrodectus species. Cannibalism started during copulation when females grasped the male’s legs with their chelicerae, and continued as females pulled the male’s abdomen onto their chelicerae, without interrupting copulation. Cannibalism was initiated by females, and not facilitated by males as was observed in other Latrodectus species. Females frequently remated however, so cannibalized males might lose paternity to future rivals. We report high rates of cannibalism, with 70 % of males killed by females during their first mating, and 85 % killed by previously-mated females. We discuss our novel findings in the context of previous observations in other Latrodectus species, proposing that foundational studies in a wider range of species are necessary to support comparative tests about the evolution of sexual cannibalism within this model taxon.

性自相残杀是性冲突的一种极端形式，可能对交配行为产生广泛的进化影响。Latrodectus蜘蛛（约有30个“寡妇”物种）可以对性相食行为的演变进行比较测试，但大多数物种的研究不多。在这里，我们描述了南美洲特有种L. mirabilis特有物种的交配和繁殖行为，重点是性食人族的发生和后果。相对于其他Latrodectus而言，交配和食人行为是新颖的物种。食人症是在雌性交配时开始的，雌性用其鞭毛抓住雄性的腿，并持续到雌性将雄性的腹部拉到其鞭毛上，而不会中断交配。同类相食是由女性发起的，而不是由其他Latrodectus物种中的男性提供的。但是雌性经常交配，因此被食人的雄性可能失去未来竞争对手的亲子关系。我们报告了自相残杀的高发生率，其中70％的男性在第一次交配时被女性杀死，而85％的女性先前被杀死。我们将在其他Latrodectus的先前观察的背景下讨论我们的新颖发现 物种，因此有必要对更广泛的物种进行基础研究，以支持在该模型分类群内进行有关食人性进化的比较测试。