Self-Castration During Sex A "Win-Win" For Male Spiders

“He achieves continuous sperm transfer after having been removed by the aggressive female, or has moved away himself. At the same time, his palp (sexual organ) plugs the female, thereby monopolizing her.”
Arachnologist Matjaz Kuntner describes the findings of a study wherein 90 percent of male spiders were observed cutting off their penises during sex, which increases the chances of successful impregnation and also of the males escaping from their mates, who generally try to eat them after copulation.