This stunning image reveals for the first time that beetles use a screw and nut mechanism for leg movement. Scientists used very high resolution X-ray imaging to prove this and found that it is widespread amongst weevils. Do you see beauty in this?
While this does allow freedom of movement, one possible disadvantage is that “when fully tightened, the joint comes to a dead stop.”
According to the authors:
We report the finding of a functional screw-and-nut system in the coxa-trochanteral joints of the legs of the Papuan weevil Trigonopterus oblongus (Pascoe) (2). We reveal the system’s structure and function through interactive three-dimensional (3D) reconstructions created from synchrotron-based x-ray microtomography (μCT) (3) of museum specimens.
The three major joints of an insect leg, the coxa-trochanteral, trochantero-femoral and femoro-tibial articulations, are usually considered as hinges (4). However, in the species of hyperdiverse Trigonopterus weevils studied here, the coxa-trochanteral joint is highly modified and allows rotational movement combined with a single-axis translation.
…apical portions of the coxae closely resemble engineered screw nuts.
It is remarkable that in the case of the weevil leg a rotary movement is accomplished by a screw-and-nut system. In engineering, such systems are mainly used for fixing connections, whereas an axle would be used for a simple rotation.