Some male spiders voluntarily "castrate" themselves during sex in order to increase their chances of fathering offspring, a new study shows.
The males break off the entire sex organ while it is still in the female, allowing it to keep injecting sperm long after they have scuttled away.
A quick getaway is understandable; the females often eat their male mates.
Writing in Biology Letters journal, a team now says castration increases the amount of sperm transferred.