The common insect called the planthopper (Issus coeleoptratus) is a real-life steampunk bug. At the point where its back legs meet at the top, there are rows of small teeth that mesh together, ensuring that the legs move in sync.
Gears allow two machines to rotate together in opposite directions. That’s exactly what the planthopper’s trochanter bumps do. Sutton tested this by pulling on the tendons of its jumping muscles with some forceps (“It’s the Serious Edition of Operation”, he says.). Even if he only pulled one tendon, both legs would extend because the gears transmitted the motion of one trochanter into the other.
“Then, we got really lucky because we saw a few jumps where the gears wouldn’t engage perfectly,” says Sutton. When this happened, one leg was partially extended before the gears finally snagged and the planthopper’s nigh-perfect coordination was ruined.
Wait! It gets better. These gears are training wheels!
Training wheels, meaning that the gear teeth are not present in the final, molted, adult version of the bug. By then, the leg pivots are smooth, but they do move together, leading scientists to believe that the insect has its legs movements well-synched by that stage. See pictures of the gears at Not Exactly Rocket Science. Link
(Image Credit: Malcolm Burrows)