Most vacationers complain to the travel agent when deadly spiders infest their warm weather getaway. Maydianne C.B. Andrade is delighted.

The Cornell graduate student spent January in the blazing heat of Western Australia, painting color codes on redback spider legs by day. At night she donned a head lamp to watch one of the most extreme forms of self-sacrifice in the animal kingdom. That's how she found (and published in the Jan. 5 issue of Science) the solution to a long-standing puzzle in evolutionary biology: the adaptive advantage of male complicity in sexual suicide and cannibalism. At last, letting oneself be eaten during mating makes sense, in an adaptive sense.

Hardly an endangered species, the redback spider (Latrodectus hasselti) is too omnipresent for comfort in parts of Australia. "Mothers warn their children not to touch the female redbacks,"Andrade said of attractively colored, jellybean-sized arachnids with a crimson blaze on their backs. Venom from a female bite can kill a child or an elderly person.

Compared to the female redback, the males aren't much to look at. So small and light (about 2 percent of the female's mass), the males might be mistaken for another species. "Males hang around the web for days or weeks, waiting for the female to mature," Andrade said.

What happens next defies logic: A "lucky" male is chosen for mating and inserts his intromittant organ. Then, as recounted in Andrade's Science article, he performs a spectacular somersault that positions his abdomen directly over the female's mouth parts. He remains there throughout copulation -- as long as half an hour. If the female is hungry enough (and they are about 65 percent of the time, according to Andrade's observations), the male is a meal.

Andrade looked for an advantage (to the male) of this behavior. In a series of painstaking experiments conducted while she was a master's degree student at the University of Toronto, she labeled the sperm of various males. That would tell her whose sperm was reaching eggs of the females, which frequently mate sequentially with more than one male. Then, with the clock running, Andrade sat back to watch a drama that would turn weaker stomachs.

Her experiments demonstrated that the longer the male has to transfer his sperm, the more eggs he fertilizes. Sometimes the female is so satisfied -- sexually and appetite-wise -- that she doesn't seek another mate. Contestant number one wins the great genetic lottery of life.

Of course he's dead, but the short-lived male would have passed away, anyway. As Andrade wrote in Science, "paternity advantages of sexual cannibalism outweigh the low cost of suicide for males. Male facilitation of cannibalism probably evolved through sexual selection as the most extreme mating gift."

This spring, while other students are sunning themselves on the beaches, Andrade will head to Florida, too. There's some extreme behavior in brown widow spiders she wants to see.