She Mates, She Kills — and That's OK With Male Brown Widows

A lot of people like their love affairs to be a little bit risky — who knows why? As 17th-century theologian Blaise Pascal and countless Pinterest quote boards have mused, "The heart has its reasons, which reason does not know."

New research suggests the same might be said for brown widow spiders (Latrodectus geometricus). This cousin of the dreaded black widow spider is a sexual cannibal — male spiders go through an elaborate rigmarole in order to coax a female into mating with them, even though there's a good chance she'll end up eating them. Lots of spiders, as well as several groups of insects, engage in this gory courtship ritual.

The study, published in the journal Animal Behaviour in March 2018 finds that while individual males of many species do their very best to avoid being snacked upon during copulation, brown widow males actually seem to go out of their way to become amuse-bouche for the mother of their children. This is evidenced by the fact that males seem to strongly prefer mating with older females. The study demonstrated this to be puzzling for a couple different reasons.

The research team introduced virgin brown widow males to females of different ages: adolescent, young adult and mature lady spiders, all were capable of reproducing, although the younger spiders were more fertile than the older ones. But the males didn't seem to know this, or else they didn't care — they spent significantly more time courting the older females than the younger ones, and paid hardly any attention to the adolescents, even though it turned out these very young females hardly ever cannibalized their mates. When given the choice, males preferred to court the oldest lady spiders, even though their chances of survival weren't good — of those who chose to mate with the most mature females, 57 percent were eaten, compared the males who mated with young adults, who were cannibalized 48 percent of the time.

The research team isn't exactly sure what could possibly possess these males to make such strange mating choices, but they think it may have something to do with female pheromones: Older females might give off a more enticing scent to trick the males into thinking they're more fertile than they are in reality.