Killer sex, literally. (Zoology).

Videotapes of yellow garden spiders show that if a female doesn't murder her mate, he'll expire during sex anyway.

"As far as we know, it's the first time anyone has shown males spontaneously dying during copulation," says Daphne J. Fairbairn of the University of California, Riverside. She's not talking about the odd heart attack among romancing fellows. Among males of the yellow garden spider, "all of them do it," she says.

Tapes of 44 Argiope aurantia males that inserted both pedipalps--their sperm-delivery structures--into their mates without getting attacked show the males' legs curling up motionless within seconds. In a different test, males' hearts stopped within 15 minutes of sex. Another male, who made his second pedipalp insertion into a nearby mealworm, also died, Fairbairn and Matthias W. Foellmer of Concordia University in Montreal, Quebec report in an upcoming Proceedings of the Royal Society of London B. The mechanism of death remains unknown.

The whole business raises interesting problems. "Imagine humans if every time teenage males had sex they died," Fairbairn says. "It seems like a bad plan for the species."

There maybe one consolation for the spider male. The researchers note that as his dead body dangles in place, it will keep other males from impregnating his mate.--S.M.