How does male black widow find mate? Follow the others

It’s a myth that female black widow spiders always kill and consume their mates. But courtship remains perilous for males, cannibalism or no. The terrain, navigated in the dark, is challenging.

The female’s web releases come-hither pheromones, but only about 12% of prospective males manage to reach it. And once there, they can expect to face male rivals competing to pass their genes on to the next generation.

Usually, this results in wild displays of machismo. The males slash the female’s webs to make them less enticing to others. They deposit “mating plugs” in the female’s body to block rival sperm.

Why not simply avoid the competition and seek out females’ webs empty of other males? But male black widows seem to thrive on the competition, according to a study published July 31 in the Proceedings of the Royal Society B: Biological Sciences. Researchers found that male black widows find potential mates faster by following the silk trails left behind by other males.

“Males have to race to find females,” said Catherine Scott, an arachnologist at the University of Toronto Scarborough in Canada and the study’s lead author. “It makes sense for them to try to use all the tricks they can to find females as soon as possible, even if there are other males that have already found her.”

Scott and her colleagues started their study by marking several males with different colors and releasing them at different distances from a large female’s web.

Most males reached the web within a couple of hours. Those that started from farther away arrived just as fast as their rivals: They simply followed the silk threads released by the males ahead of them.

“The silk threads act like a highway connecting the tops of plants,” Scott said. “So following this path is more efficient than trying to make their own way, climbing over obstacles and making sure they are still going in the right direction just based on pheromones carried by the wind.”