PopSci's Fourth Annual Brilliant 10

Maydianne Andrade

University of Toronto at Scarborough

She scrutinizes cannibalistic spiders to understand the twisted net of sexual selection.

Life sucks if you're a male Australian redback spider. Latrodectus hasselti isn't the only animal to engage in postconnubial cannibalism (a practice in which females eat the males immediately after mating), but it may be the only species in which the male offers himself voluntarily as a snack. This so-called "sacrificial somersault" occurs when the male inserts one of his sperm-transfer organs into the female, then pivots in a forward "handstand" so that his body hangs over the female's jaws. While he's transferring sperm, the female, who by the way is 200 times as large as he is, chomps on his rear end. If he's lucky, he'll survive for a second mating. If not, well, he won't be around to care.

The scientific champion of these S&M arthropods is biologist Maydianne Andrade, 35. Andrade first encountered the redback-whose lethal bite gives it as infamous a reputation in Australia as the black widow enjoys here in North America-when her grad-school adviser asked her to go to Perth to study them. Because redbacks are nocturnal, she spent much of her time bicycling to study sites at 2 in the morning and sitting for hours under webs with a poisonous spider inches from her face. (Her parents worried so much about her safety that she didn't have the heart to tell them how often she had to dodge drunk guys wandering the early-morning streets after the bars had closed.) In the sort of scientific coup most biologists merely dream of, Andrade, while still a grad student, made a discovery so unusual that the prestigious journal Science published the research. Her finding: Although suicide does not seem the best way to spread one's genes around, redback males that get eaten by their partners actually mate much longer-and hence father more spiderlings-than their uncannibalized brethren.

Andrade's further research has proved that the spiders' mating rituals are even more complicated than they appear. Females sometimes preemptively eat obstreperous males before they finish mating. Males, for their part, develop a constriction in their abdomen during courtship that allows them to survive the first mating long enough to try for a second. Andrade is now attempting to develop a DNA library for the redback. Currently it's impossible to test the paternity of spiderlings-and thus Andrade's latest theories of mate choice and genetic control-via DNA, because the molecular tools don't exist.

Unlike her test subjects, Andrade and her own mate, husband Andrew Mason, cooperate quite well (they have adjoining labs; Mason studies the bioacoustics of parasitic flies and wolf spiders). Observing redbacks may seem an obscure choice of occupation, but the spider's life cycle has wider implications, as mate choice and sperm competition occur in almost every animal species. By analyzing suicide, cannibalism and other perverse behaviors, Andrade says, "you can test the limits of behavior at the extremes."

-Martha Harbison