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Touching

A new paper on how assassin bugs play on the web strings of spiders to lure them to their untimely end got a lot of publicity this week for good reason: "aggressive mimicry," in which a predator imitates something (for example, prey or a potential mate) that its prey is instinctively primed to approach, is intriguing on a number of counts. The paper, by Anne Wignall and Phillip Taylor of Macquarie University in Australia, details experiments they conducted to discover how the araneophagic Stenolemus bituberus tricks spiders into coming along the web to have a closer look. Mark Kinver at the BBC, Duncan Geere at Wired Science, and Jennifer Viegas at Discovery News all have good summaries.

But these summaries all focus on the assassin bug and its remarkably skillful underhandedness. I can't help but focus on the spider. (And I can't tell whether this is entirely due to my immersion in Spider Silk or also, I suspect, to reading The Wide Sargasso Sea and seeing Rosencrantz and Guildenstern Are Dead at a particularly impressionable age.) Wignall and Taylor's experiments show that there are measurable differences between the vibrations set off by vinegar flies or aphids (the regular prey of the spider they were testing) caught in a web, by debris falling into a web, and by male spiders performing courting behaviors on a web. In addition, there are differences between the vibrations produced by flies or aphids that have just hit the web and those produced by flies and aphids that have exhausted themselves in their struggle with the web. These experiments confirm that spiders are exquisitely sensitive to movement on their webs. They don't just rush toward the source of any old vibration, assuming it means food. Instead, Wignall and Taylor showed that the spiders in their experiments discriminated beween these vibrations and responded accordingly. Debris hitting the web: the spiders sat still. Courting male on the web: the female spiders assumed a come-hither stance. Prey struggling in the web: the spiders faced their prey and approached it bit by bit. Spiders are capable of turning the tables on assassin bugs by rushing them and getting their fangs in before the assassin bug can attack. But they hardly ever do. Unfortunately for spiders lured by assassin bugs, as you can see in the video below, a bit-by-bit approach is fatal.

As far as I know Wignall and Taylor are behavioral and evolutionary biologists, with no pretensions to cinema. But I find this film of theirs, reminiscent of Indonesian shadow plays, hauntingly Shakespearean.




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