Male Black Widow Spiders Destroy Female’s Web to Deter Rivals; New Study Shows Home-Wrecking Behavior Could Protect Females from Harassment

Male black widow spiders destroy large sections of the female’s web during courtship and wrap it up in their own silk. New research recently published online in an open-access article in Animal Behaviour shows that this home-wrecking behavior deters rival males, by making the female’s web less attractive to them. The article is titled “Web Reduction by Courting Male Black Widows Renders Pheromone-Emitting Females' Webs Less Attractive to Rival Males.” Surprisingly, the females don’t seem to mind the destruction. The authors of the study, from Simon Fraser University in Canada, say the males’ behavior could protect 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 (image) are approximately 15 mm 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,” said Dr. Catherine Scott, lead author of the study. “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.” Competition for females is fierce: as many as 40 male suitors may arrive at a female’s web in one night. Because of this, males have developed ways to fend off the competition, such as guarding females and applying mating plugs.
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