Male Spider Uses 'Courtship Vibrations' When Mating To Avoid Being Eaten
There's a kind of spider, of the genus Argiope, that has to perform a little dance before approaching a potential mate. Otherwise, she'll eat him. Spider sexual cannibalism, in which spiders eat each other before, during, or after sex, is actually pretty common. Often, it involves females consuming male seducers, and often, the males don't even put up a fight.
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But research published this summer in the journal Scientific Reports has explored the mechanics of Argiope's hypnotizing foreplay, which lulls the potential mate/assailant. "Male web-building spiders face a significant problem: how to begin courting female spiders without being mistaken for prey?" the scientists reported. "Male Argiope spiders generate distinctive courtship vibrations (shudders) when entering a female's web." For some reason — they aren't sure exactly why — the vibrations delay the female from consuming web intruders.
Even in jargony, scientific terms, talk of spider cannibalism can be disturbing. Here's UC Berkeley's Kenwyn Blake Suttle talking about the history of sexual cannibalism research: "It is easy to imagine the evolution of sexual cannibalism as an adaptive female strategy," he writes. "Females can gain nutritional benefits and resulting increases in fecundity by consuming their mates. Male complicity (i.e. suicide) is a more difficult scenario to reconcile, because in sacrificing their soma to females, males forfeit any future mating opportunities and subsequent fitness benefits."
Arachnologists have been studying that conundrum for years. But the male Argiope apparently doesn't subscribe to the suicidal tendencies of his eight-legged peers. He wants babies, but he's no martyr. The Argiope won't enter a female's web unless he has performed a shudder dance that sends vibrations across the web. Scientists have wondered what the effect was. Does it let her know he was a spider, like her? That he means her well, not harm? ("Spider here, don't mind me.") Scientists sought to answer these questions by simulating the vibrations while a live cricket was stuck in the web. They found that the females didn't eat the crickets as quickly when under the spell of the vibrations as when all was quiet. Scientists did the same thing when a male spider was in the web, and the female reacted similarly, indicating the practice wasn't a form of species identification.
"These results suggest that male web-building spiders employ a ... vibratory signal to ameliorate the risk of pre-copulatory cannibalism," the researchers concluded. The vibrations cut the risk, but they don't solve the problem. Eventually, the female ate the crickets, vibration or not.
Above photo courtesy of Shutterstock
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