Male black widow spiders take courtship to a whole 'nother level.
Researchers from Simon Fraser University in Canada found that for these eight-legged arthropods, courting sometimes mean "visiting a female's web and ripping it to shred" to fend off competition, CBS News reported. This home-wrecking behavior not only deters rival males, but it also protects the female from harassment, enabling her to get on with parenting.
The western black widow spider -- Latrodectus hesperus -- is native to western North America. Female black widows are around 15mm long and black, with a distinctive red hourglass-shaped mark on the abdomen. The male is much smaller, and a lighter tan color with a striped abdomen. Black widows build messy webs, which they use to communicate via vibrations and pheromones.
"The silk pheromones that female black widows produce are like scent-based personal ads," Catherine Scott, lead author of the study, said in a statement. "One whiff of the pheromone can tell a male about the age, mating history and even hunger level of the female. These complex chemical messages are just one part of the spiders' communication system, and web reduction is a fascinating behavior that allows a male to interfere with a female's message."
For the study, Scott and her colleagues conducted a series of experiments where they let female western black widow spiders build webs in cages in the lab over the course of a week, and then took those cages to a beach on Vancouver Island where the spiders are found naturally, UPI reported. They compared the number of wild males arriving at cages containing three different kinds of web: intact webs, webs with about half of the silk cut out and bundled up by males, and webs from which half the silk was cut with scissors and removed.
They found that intact webs had attracted three times as many spiders than "webs that had already been partially sabotaged by destructive males," UPI reported. The webs that the researchers reduced were just as attractive as the intact webs, suggesting it's more complex than just reducing the surface area of the web.
"Whatever the males are doing during web reduction is much more effective than simply reducing the amount of silk by half," Scott said. "One possibility is that the female pheromone is concentrated in certain areas of the web, and males are bundling up those specific sections with silk, which stops the pheromone from being released. The males could also be adding their own pheromones, which rival males avoid. We didn't find evidence for a male silk pheromone in these experiments, but it's definitely something we want to investigate further."
Researchers said one reason female black widows tolerate the destruction of their webs may be because behavior is helpful to them.
The findings are detailed in the journal Animal Behavior.
