Toss a piece of leaf onto a spiderweb. The spider is indifferent. Because leaves don't squirm like captured flies. But Australia's "assassin bug" turns the tables on spiders. It exploits their keen sense for vibrations by mimicking the movements of prey—luring unwitting spiders into striking range.
Researchers observed how spiders reacted to various visitors to their webs—like leaf fragments, courting males, prey like flies, and the assassin bugs. The spiders ignored leaves, and assumed mating position for males. But they approached assassin bugs just as if they were investigating a juicy fly.
Then the researchers analyzed the frequency, duration and amplitude of each visitor's vibrations. And they found that assassin bug's vibes most closely matched some of those of prey. When prey struggle violently, spiders rush to subdue them—a potentially dangerous situation for assassin bugs. So the bugs have learned to gently pluck the silk strands, to mimic only the unthreatening leg twitches of exhausted prey. The research is in the journal Proceedings of the Royal Society B. [Anne Wignall and Phillip Taylor, "Assassin bug uses aggressive mimicry to lure spider prey"]
The assassin bug’s choice of vibrations maximizes the chances that the spider, while still behaving like the hunter, becomes the hunted.
—Christopher Intagliata
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