Flirty Female Spiders Use Silk to Capture a Male's Interest

When male wolf spiders don't seem that interested in a female wolf spider, she ups her game by releasing more pheromone-rich silk.

New research suggests we're missing out on learning about the dramatic lives of spiders. In addition to cannibalism, ambushes, and the devouring of young, the study finds that when it comes to love, female wolf spiders take things into their own hands.

The arachnids actively seduce males using their silk, a rarely observed phenomenon in the spider world, scientists reported this month in the journal Ethology.

Many species of wolf spiders are common throughout streams, forests, and agricultural fields like soybean farms in the U.S., Canada, and Mexico. Head out into a field in the early morning, and it'll be covered in silk, says Matt Persons, an arachnologist at Susquehanna University in Selinsgrove, Pennsylvania.

"[The silk] isn't a waste product," the lead study author explains—"it's an internet, a communication network." And he's spent 24 years trying to figure out what the spiders are saying to each other.

He's Just Not That Into You
In the case of female thin-legged wolf spiders (Pardosa milvina), some of those communiqués include flirting.

Laboratory trials with males and females of this species revealed that females confronted with males that were courting half-heartedly or not at all increased their production of dragline silk—a type of silk employed to break a fall.
These pheromone-laden strands also impart all kinds of information about its weaver to a spider that can read the cues.

In the experiments, females faced with an enthusiastic male or silk from another female didn't produce as much dragline silk.

Spider silk as seen through a scanning electron microscope. [Photograph By Chris Latanich]

"Often, we think about males courting and females choosing amongst the males," Persons says. The female is fairly passive in this context since it's the male that's doing all the jumping up and down and arm—or leg—waving. "That's been the paradigm since [Charles] Darwin," the spider biologist explains.

But this study shows that that's not always the case. By pumping out more dragline silk strands in the face of apathy, females are likely encouraging uninterested males. Mating in these thin-legged wolf spiders could be more akin to a dialogue between partners rather than a take-it or leave-it choice for the females, Persons says.
It's clear that these females respond to uninterested males, he says. His next step is to see if the males respond to this flirting by upping their courtship behavior.

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