Male wasp spiders have figured out a cure for their mates; wandering eyes: During sex, they break off a piece of their male organ, and use it as a "chastity belt" to plug up the female's genital opening, says New Scientist. German reseearchers studying the wasp spiders noticed that virgin females had sex much longer than those who had previously mated, and so they took a closer look at what was going on. They realized that males were breaking off part of their pedipalp, which delivers sperm, and leaving it behind to thwart future rivals. The detached tip doesn't completely prevent further intercourse, said researcher Stefan Nesler, but it "lugs the orifice so securely that the transfer of semen is probably largely excluded."
That ensures the female will give birth to offspring of the first male on the scene, and not those of her subsequent boyfriends.