No one—but no one—likes to get killed for having sex, and as that is often the fate of male black widow spiders, the critters are evolving a mating tactic that is, anthropomorphically speaking, more than a little creepy. Researchers found a startling, and slightly unsettling, mating shift in a study titled "Copulation with immature females increases male fitness in cannibalistic widow spiders," published in Biology Letters and translated into English as "Dirty old men spiders avoid violent death, increase number of babymamas by chasing jailbait female spiders." Essentially, Gizmodo notes, the males of the species have noticed that they keep getting killed when mating with sexually mature females. But if they chase young spider-skirt, the immature females aren't capable of killing them.
Here's how it works: The young females' reproductive organs are functional, but internal, and protected by an exoskeleton. The dirty old man spiders cut through the exoskeleton with their fangs, and leave a special sperm delivery in the female's sperm receptacle. It's a narrow window in her development, but when the female matures, she pops out the male's spider babies. Writes Gizmodo: "Spider sex with minors isn’t a rare occurrence. When the researchers went out into the field to collect immature females, they found that one-third of them had been violated in this way." It's an evolutionary win-win for the male, who is a) still alive, and b) free to go out and mate again, thereby increasing his progeny. (Here's a graphic description of what it's like to get bitten by a black widow. Hint: Not fun.)