Male Black Widows Send Sweet 'Whispers' to Females to Say They're Not Prey

When male black widow spiders are in the mood for some loving, they shake their abdomens to produce carefully pitched vibrations that let females know they've come to mate and are not potential prey, according to new research.

Doing so is a necessity for males entering the female's web, as the wrong moves could signal to the female that the creature crawling in her web is her next meal rather than her next mate. (Though sometimes, the occasion is one in the same. Female black widows do eat their mates, but it is not typical.)

"The web functions as an extension of the spider's exquisitely tuned sensory system, allowing her to very quickly detect and respond to prey coming into contact with her silk," said Catherine Scott, a graduate student of biology at Simon Fraser University who participated in the research.

"This presents prospective mates with a real challenge when they first arrive at a female's web: they need to signal their presence and desirability, without triggering the female's predatory response."

Scott, along with fellow graduate student Samantha Vibert and SFU biology professor Gerhard Gries, recorded the vibrations made by male black widow spiders (Latrodectus hesperus), hobo spiders (Tegenaria agrestis) and prey insects such as house flies and crickets while in the web of a female black widow.

The research team found that the courtship vibrations of both male black widows and the hobo spider was different than vibrations made by prey, but that "the very low-amplitude vibratory signals produced when male black widows shake their abdomens were particularly distinctive. "

"These 'whispers' may help to avoid potential attacks from the females they are wooing," Scott suggested.

The research is published in the journal Frontiers in Zoology

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