Voracious male spiders that kill adult females of their own species (genera Walckenaeria, Diplostyla, Neriene, Meta, Araneae)

In contrast to the popular belief that adult female spiders often kill and eat their adult male partners in the context of copulation, we present a few instances of adult male spiders killing and eating adult females of their own species in the laboratory. However, in line with the popular belief, we also found a few instances of adult females killing adult males of their own species. In spite of the fact that our experiments during the last decade focused on inter-specific killing among spiders of unlike species, we found some adult males killing and eating their conspecific adult females when we tried to get offspring from females fertilised in the laboratory. In addition to data of male-killing-female and female-killing-male, we further, present instances of adult and younger male spiders killing and eating male and other conspecifics. We also give such data for females. Our laboratory data ask for an explanation of the possible reproductive benefit in the males that miss the chance of getting own offspring (own gene replicates) from the conspecific females they treat as a prey item. We give three reasons that can explain why male spiders benefit from killing females of their own species by referring to sociobiological explanations.