After placing a dozen maggots in a petri dish, Michael Wise was surprised to see that only two were still there. The rest had made a break for it, and were jumping all over his lab.
Wise, a botanist at Roanoke College, had been studying gall midges—flies that lay their eggs inside silverrod and goldenrod plants. Once the eggs hatch, the developing larvae create abnormal swellings called galls. Wise would dissect these and collect the orange, rice-size maggots within. And he noted that they’d often start jumping: out of the galls, out of his hands, out of petri dishes. How, he wondered, could a legless animal jump at all, let alone so far or so quickly?
Fortunately, he knew exactly whom to call. Wise had gone to graduate school with Sheila Patek, a biologist at Duke University, who has studied the record-breaking punch of the mantis shrimp and the ballistic jaws of the trap-jaw ant. “A lot of people know that I study small, fast things, so I get a lot of requests to film random stuff,” Patek says. “I’m almost always up for it.”
But many animal movements that people think are really fast “are not actually that fast,” she says. To film a fish’s strike or a grasshopper’s leap, you can get away with a high-speed camera that shoots at a paltry 1,000 frames per second. To film the gall-midge maggots, Patek had to break out her 20,000-frame-per-second hardware. “They jump at the same speed as fleas—insects that are using legs,” she says. “They’re really good.”
Despite the maggots’ speed, “I don’t think they have any aiming capability,” says Patek’s colleague Grace Farley. To film them, Farley placed one larva at a time in a petri dish and looked for the moment when it drew its head and tail together in preparation for takeoff. When that happened, Farley rotated the dish so the larva was at least pointing in the right direction. (It didn’t always work, but since high-speed video files are very large, and bad footage is usually discarded, to my great disappointment, Farley has no maggot blooper reel.)
The maggot’s technique, as revealed by the footage, is surprisingly complicated. When it loops its body, it unites two patches of microscopic hairs—one just behind its head and one on its tail. When these touch, they stick. The maggot then pumps its own internal fluids into the back third of its body, turning it into a swollen strut that Farley calls a “transient leg.” The pressure builds in the leg until it overcomes the sticky forces holding the head and tail together. The maggot releases itself, the leg pushes downward, and the whole animal explodes upward. “It shows how even squishy forms can effectively act as rigid limbs,” says Talia Moore from the University of Michigan, who wasn’t involved in the study.
The team showed that the maggots can jump as much as five inches. That’s more than 36 times their body length, and akin to a human leaping more than 200 feet. They’re extremely efficient too: It would take 28 times as much energy to crawl across the distance that they can cover in a single jump. In the wild, this prodigious leaping ability is a lifesaver. If the gall is breached, the larvae can bounce to safety. And many species deliberately leave the galls once they’re old enough; they fall to the ground and leap around randomly until they land on dark, moist soil where they can transform into adults.
Many other animals can jump without legs. Springtails—tiny relatives of insects—push a special appendage underneath their tails against the ground. Click beetles jump by lying on their backs and violently snapping their heads against a surface. Some snakes, such as the jumping pit viper and brown sipo, can fully launch themselves off the ground. One fictional mammal transforms its tail into a spring.
In all these cases, a hard body part acts as an erstwhile limb. By comparison, “the lack of a complex musculoskeletal system in the midge larvae makes jumping quite impressive,” says Moore. Other soft-bodied, wormlike animals can also take to the air in the same way: They curl into a loop, latch themselves in place, pressurize part of their own bodies, and take off. Other fly larvae do this, as do nematode worms. The latter are so small that they don’t even need sticky hairs; they can latch their heads and tails together through the surface tension of the water that covers their bodies.
Many of these legless jumpers belong to groups that are incredibly rich in species, so this style of movement may actually be more common than the limb-propelled hops of locusts or kangaroos. “It could be a way of locomotion that’s even more fundamental than grasshopper legs,” says Patek. “I think it’s widespread, and we just haven’t been looking.”
The secrets of these squishy jumpers might help engineers develop more durable robots for, say, search-and-rescue missions. “One thing engineering is really not good at is making small, extremely high-acceleration devices that don’t self-destruct and can be used over and over again,” says Patek. Abandoning hard materials for soft ones might solve that problem, provided that said soft robots could be made to move in useful ways.
“Robots with soft bodies can be more difficult to destroy, which would give us a great advantage if we want these robots to work in unstructured environments like an earthquake zone,” says Zeynep Temel from Carnegie Mellon University, who develops robots inspired by biology. And as the gall-midge maggots show, you don’t have to sacrifice mobility or efficiency for the sake of a little softness.
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