Some male spiders tie up females before sex so they don't get eaten alive

Spider cannibalism — the tendency for female spiders to eat their mates during or after sex — is fairly common knowledge at this point. There's a surprising evolutionary benefit to this copulatory suicide, too, as Ed Yong explained in National Geographic in 2016:

In 1996, Maydianne Andrade found that sexual encounters between redback spiders are longer if the male allows himself to be cannibalized. By sacrificing his life, he can fill his partner with more sperm. The female keeps that sperm in two storage organs, and can control when she uses those stockpiled cells to fertilize her eggs. If she mates again, the second male's sperm might displace those of the first now deceased suitor. But Andrade showed that females that eat their first mate are more likely to reject a subsequent one.

So, by committing "copulatory suicide," the males guarantee their future fatherhood.

In that same article, Yong also explains how some male widow spiders "can use their fangs to create openings in the [immature] females' outer shells and access their genitals."

But this, apparently, is not the only way for a male spider to live to fuck another day. According to a new study in the Journal of Animal Behavior, focusing on the Thanatus fabricii spider:

We found that males always bit and bound females before and during mating. The bitten females quickly fell into a state of immobility, during which males copulated with them. […] Binding by silk prolonged the state of immobilization, allowing males to perform more insertions. After copulation, females were less successful in catching their prey (ants), suggesting that this mating strategy negatively affects female fitness.

Essentially, the male spiders drug and bound the females in order to ensure their survival. "Spiders sometimes spend hours luring females to court them, but these guys just go and bite," explained Lenka Sentenská, one of the study's authors, to New Scientist.

That being said, it's not clear if this behavior is necessarily coercive (read: rape-y), or if the sedation is actually a sign from the females that they are "receptive" to being mated with. "Females that fall into the state of immobility will allow the male to mate, while unreceptive females will continue struggling and thus will reject the male," it says in the paper.

Also: in 11 percent of observed cases, the male spiders failed to immobilize the female, and ended up dead anyway.

Biting and binding: an exclusive coercive mating strategy of males in a philodromid spider [Lenka Sentenská, Ondrej Šedo, and Stano Pekára / Journal of Animal Behavior]

Some male spiders tie up females before mating to avoid being eaten [Joshua Rapp Learn / New Scientist]

Image: JJ Harrison / Wikimedia Commons (CC 3.0)