Extreme bounce saves spider male life after sex


The researchers studied 155 pairs of spiders. 152 males successfully hopped away. Only three failed to make the jump and were eaten immediately. In order to determine whether the jumping ability of the male spiders really makes the difference between life and death, the researchers used a fine brush to attach several male spiders to their female partners. These experimental spiders were all eaten.

Surprisingly, the escaped males return to their cannibalistic mates. Because when mating, they attach a kind of safety line made of spider silk to the female. After initially jumping away, they crawled back along the leash to mate again. The animals can repeat this cycle up to six times. The behavior may seem reckless, but the male spiders want to be sure that they have actually fertilized the female.

How can sexual cannibalism be explained in evolutionary terms?

At first glance, sexual cannibalism doesn’t seem logical, but the behavior makes evolutionary sense, explains biologist Matthias Foellmer, who researches the topic at Adelphi University. In most species of spiders, the male would not contribute much to the offspring apart from his seminal fluid. “So why shouldn’t the female eat it?” says Foellmer, who wasn’t involved in the new study. “When you think about it, it’s amazing it doesn’t happen that much more often.”



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