Gear is an important transmission device in man-made machinery, and it can also be found in nature. Natural gears come from insects called Issus coleoptratus, and these gears grow on their legs, like this:

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this is what natural gears look like under an electron microscope. They grow on the nymphs of the sheath-winged ladycicada. The meshing of the gears in the legs allows them to quickly prepare-eject in 30 microseconds, making a precise jump.

dynamic chart:

the rotation speed of the two gears is more than 33000 revolutions per minute, and the acceleration of gear rotation is 700g. This is the first example of a "biological gear" found so far. Of course, if it is said to be jagged structure, there are still many, like the following wheel back bug also grow gears on the back, but this "gear" is not useful:

after talking about gears, are there any wheels in nature? If the "micro wheel" on a molecular scale is also counted, it can be said that there is. For more information, please read the original text.