Biological screw

Researchers of the SMNK discover biological screw in a beetle´s leg

Entomologists Thomas van de Kamp and Alexander Riedel report in the renowed journal „Science“ on the discovery of a screw-and-nut system in the leg joint of a weevil. 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 corresponding 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 possess a greater dorso-ventral mobility, which is ideal for life on twigs and foliage.