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  • Richard Conniff writes about behavior, in humans and other animals, on two, four, six, and eight legs, plus the occasional slither.

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Properly Screwed-Together Beetle

Posted by Richard Conniff on June 30, 2011

Papuan weevil

I don’t think you can call this biomimicry, since humans invented the screw sometime around the third century B.C., and this is the first we’ve heard that the Papuan weevil got there first.

So maybe it’s more like convergent evolution, two species arriving independently at the same solution.  In any case, I like the mechanical nature of the discovery.  I have vivid memories of watching Dr. Denton Cooley perform heart surgery, and being struck by how mechanical it seemed, with veins being 45’d together the way a carpenter 45’s a joint, and lines being threaded through blind spaces the way an electrician will run a wire with a fish tape.  So this further instance of the mechanistic way things get put together also pleases me.  Here’s the press release from this week’s Science:

Many innovations in modern mechanical engineering were taken directly from nature, like the ball-and-socket joint, which was first described as part of an organism’s anatomy before being adapted as a machine. The classic screw-and-nut system, however, was thought to be a uniquely human innovation. Now, researchers have found an example of this screw-and-nut system in the legs of a beetle known as the Papuan weevil, Trigonopterus oblongus. (Apparently, evolution beat us to the punch on that one as well.) In a Brevium, Thomas van de Kamp and colleagues describe this functional screw-and-nut system in the weevil’s coxa-trochanteral joints, one of the three major sets of joints in an insect’s leg.  Until now, these particular joints were considered to be hinges. But, according to the researchers, the tips of the insect’s coxae closely resemble nuts with well-defined inner threads that continue internally for 345 degrees and the corresp onding trochanters have perfectly compatible external threads that cover 410 degrees. They suggest that an advantage of this system may be that the weevil’s legs come to a stable resting position, which is ideal for life on twigs and foliage.

Half the weevil's leg joint with external screw thread

The other half has an internal screw thread


One Response to “Properly Screwed-Together Beetle”

  1. …….Properly Screwed-Together.

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