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.