Attracted to female cannibal spiders

THE scent of a dead rival  might not seem like much of  an aphrodisiac, but for the Pennsylvania grass spider, it’s exactly what males look for in a mate. They are far more likely to approach a female if she has recently killed and eaten a male. Jonathan Pruitt and colleagues at the University of Pittsburgh in Pennsylvania captured young spiders (Agelenopsis pennsylvanica) from hedgerows and took them back to the lab. The team selected 100 females and gave 50 of them a wounded male to kill and eat; the other 50 dined on a cricket. Some 10 to 24 days later,  Pruitt’s team gave 20 male spiders a choice: to approach the web of a cannibalistic female, or that of a female that hadn’t consumed a male. Three-quarters of the males headed towards the cannibal (Ethology, doi.org/rsm). “A history of cannibalism makes females more attractive to subsequent suitors,” says Pruitt. He found that females typically ate only one male during the lab experiments, and speculates that males are aware of this and so feel more confident approaching a known cannibal.