Male Black Widow Spiders Try to Avoid Sex That Will Kill Them

By Joseph Castro | July 6, 2011 4:17 pm

spacing is important

Sometimes sex just isn’t worth your life.

For male black widow spiders, standing at just a quarter of the size of their mates, sex involves a very real danger: females of the species have no qualms about turning cannibalistic if they’re hungry after getting down and dirty. But it seems that it’s more than just a game of chance for horny male spiders. Researchers at Arizona State University have now learned that simply walking on the webs of female spiders can provide males with chemical cues telling them if their potential mates are ravenous enough to eat them.

In the study published in the journal Animal Behavior, researchers routinely fed one group of female spiders for several weeks while starving another group (noticeably shrinking their sizes). They then looked at the courtship behavior of the male spiders in a series of tests. In the first experiment, the researchers placed the males on the females’ webs while the cannibals were absent. Here, the males were far more likely to begin their courtship rituals on the webs of cricket-full females.

A male’s courtship dance, the researchers explained, lasts an hour or two and involves tapping different areas of the web. “It’s like spider tai chi; by waving his legs and plucking, he’s providing vibrations that are very distinct to tell the female, ‘I am not a prey item,’” lead author James Chadwick Johnson told BBC Nature.

To make sure that the males were only picking up cues from the silk—and not taking the obvious hints from the dead bodies scattered about—the researchers presented the male spiders with web-wrapped toothpicks cleaned of any leftover food. Again, the males liked the silk of satiated females.

In other tests, the males reacted similarly when the females were present; and in a final experiment, the researchers tried to trick the male spiders by mismatching the females and their webs (well-fed females on the webs of starving females and vice versa). It didn’t work most of the time—males chose the fattened females, suggesting that males pick up stronger chemical cues from the actual spiders than from their webs.

It’s important to note that while the male black widow spiders preferred the well-fed females, they didn’t shun the hungry spiders altogether, though they’re probably regretting it now in spider heaven. Five out of seven starved females attacked their mates after sex, with three of the females successfully killing their foolish mates. Comparatively, none of the satisfied females attacked their mates.

But one still has to wonder: Are the males really valuing their lives, or do they just prefer their lady-spiders nice and plump?

(via BBC Nature)

Image: Flickr/laurence_grayson

  • B. Neuenschwander

    *Male Black Widow Spiders Try to Avoid Death by Snoo Snoo

  • Chrisj

    I’d have thought that a well-fed female is a better bet reproductively, as she’s likely to have more energy to devote to egg-manufacture. So yes, interesting research, but as you say, the conclusions are still somewhat open.

  • MikeK

    Male widow spiders may just like big butts.

  • Devin Carroll

    Why is the photo of a different species? It looks like the red-backed widow, Latrodectus hasselti. In Arizona they were probably using Latrodectus hesperus, which has red only on the belly.

  • Karen

    Not a scientist but an Aussie that has squashed a lot in her time and that looks like an Australian Redback spider to me. Also the female redback spiders are the striking black with bright red back, the males have a duller colouring, so I suspect your photo is of a female redback spider.

  • Georgia

    Australian redback spiders are a type of black widow – all black widows have the hourglass marking on their belly. Different species of black widow may also have additional markings.

  • Kevin

    I live in North Carolina and I recently found a big black widow that has a prominent red stripe on her back just like the one pictured here. She also has the typical hourglass on her abdomen. I had never seen one before with a stripe on the back, so I’m wondering if the one I found is the common black widow native to North America, or have I possibly found an introduced Australian redback? With global commerce these things do hitch rides to new territory, after all.

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