A Biological Screw in a Beetle’s Leg
Joints on the legs of weevils form a functional screw-and-nut system. The coxa-trochanteral joints on the legs of the weevil Trigonopterus oblongus (Pascoe) work as a biological screw-and-nut system. The apical portions of the coxae closely resemble nuts with well-defined inner threads covering 345°. The corresponding trochanters have perfectly compatible external spiral threads of 410°.