Insect uses 'gears' to jump, study finds
The leaps of baby plant-hopping bugs are powered by tiny structures that look remarkably like mechanical gears, new research shows.
The rapid jumps of baby plant-hopping insects are powered by structures in their legs that look and work like human-made mechanical gears, a new study suggests.Skip to next paragraph
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The finding, detailed in this week's issue of the journal Science, reveals a remarkable case of similar evolution in animals and machines, scientists say.
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Burrows and his colleague Gregory Sutton were studying how insects manage to jump so quickly when they turned their attention to a species found in gardens across Europe called Issus coleoptratus, also known as the planthopper.
When the pair studied immature forms, or nymphs, of the insect, they discovered protruding, teeth-like structures on their hind-leg joints.
"We thought, well, that's pretty weird," Burrows recalled.
Upon closer examination using a microscope, the "teeth" were revealed to be part of curved gear- or cog-like strips found on each hind leg. And just like a cog, the teeth appeared to intermesh with one other, like on the gears of a bicycle.
"We were totally dumbfounded when we saw this," Burrows said.
The scientists' astonishment grew when they took high-speed video of live planthoppers and watched as the gear teeth of the insect's opposing hind legs locked together and rotated in preparation for a jump.
"You could see these gear wheels moving past each other, just like a man-made gear wheel. It was extraordinary," Burrows said.
The video also revealed that this mechanism worked to couple the insect's legs to a remarkable degree: when one leg moved, its cog firmly engages with its counterpart on the other leg, turning it and causing it to move by the exact same amount.
The end result is that both legs are synchronized to within 30 millionths of a second of one another.
Such synchrony would be very difficult to achieve using only the insect's nervous system, Burrows said. "The nervous system uses neural impulses with durations of one to two milliseconds — much longer than the 30 microseconds we observed."
Baby planthoppers require this level of precision when jumping because even tiny discrepancies between their two legs would impart a sideways twist and spin the insects out of control.
"They're going incredibly fast," Burrows said. "In one millisecond, they're going from zero velocity to about 12 mph."