Unlike grasshoppers, whose legs are located on the sides of its trunk, Issus' legs lie beneath its body. That creates a problem. Whereas a grasshopper can push off with one leg and still hop straight, a planthopper that tried jumping with just one leg would spin rapidly around the axis of its body.
Instead, the insect's two rear legs move with remarkable coordination.
To better understand how, Burrows and colleague Gregory Sutton took high-speed videos that captured up to 30,000 frames each second of Issus nymphs as they jumped.
The images showed that the insect's two hindlegs always moved within 30 microseconds of each other. A microsecond is one millionth of a second, and 30 microseconds is significantly less time than it takes for a single nerve impulse to reach the muscles in the animal's legs.
Because their nervous systems are too slow to synchronize movement of the hind legs, the insects have developed a mechanical solution. Close-up high-speed images revealed gear wheels on each hind leg with about a dozen teeth that interlock, the researchers report today in the journal Science. These gears ensure that the force of movement transfers almost instantly from one leg to the other.