Have you ever seen those really tiny insects scatter everywhere when you walk through grass? Planthoppers (Issus coeleoptratus) are able to jump at tremendous heights in relation to their body, and can jump up to one foot. For a 1 mm long bug, that’s impressive! But how do they do it?
Gregory Sutton and Malcolm Burrows from the University of Cambridge discovered that there are gears inside their leg joints, so that the legs move simultaneously, giving the most bang for the buck so to speak. They have been studying insects like fleas and planthoppers for 10 years, trying to discover how the insects’ legs are able to move within 30 microseconds of each other. The coordination would take more than their nervous systems could handle. After much research, the answer was found in a footnote of a handbook. In the ’50’s, scientists had noted that young planthoppers have small bumps on the first segment of their hind legs.
Burrows and Sutton discovered the function of the bumps by planthoppers that had been restrained on their backs. The insects would try to jump whenever the duo gently prodded their abdomens. Just before their legs shot out, their trochanters would squeeze together. The bumps engaged and rolled against each other, exactly like man-made gears. “I was gobsmacked,” says Sutton.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.
However, that was only with the juveniles. How do the adults jump even higher? Click here to find out.
(via National Geographic)