Going Ballistic

The ballistic trajectory of a leaping gall midge larvae

Reproduced with permission of Journal of Experimental Biology

The legless larvae of a species of soft-bodied midge can spring into the air and travel a distance thirty-six times their body length. Legless leaping has evolved multiple times, but the biomechanics of this yet-undescribed species were of particular interest to an international team of scientists.

The team, led by Grace Farley and Sheila Patek at Duke University, with colleagues in the United States, United Kingdom, and Germany, studied the jumping mechanism of the midge Asphondylia sp. These three-millimeter-long larvae live in the galls of goldenrod plants and start jumping as soon as their protective casing is lost. Researchers opened the galls and recorded the jumping with a high-speed video camera that could capture 20,000 frames per second. They used observations captured on film to examine jump preparation, launch and takeoff dynamics, as well as horizontal travel distance, energetics, and body positioning.

The videos showed that, before launching, the worm-like larvae bend their body to form an adhesive latch linking head to tail. Then, contracting their muscles, the larvae exert enough pressure that the latch is released, generating the jump. Latching provides the recoil motion that launches larvae into the air in a ballistic pattern. Their take off velocity averages 0.85 m/s—similar to that of fleas, though only half as speedy as leggier, hard-cuticled grasshoppers. Nevertheless, it is “pretty impressive” for something that is essentially “a soft ball of mush,” said co-author Greg Sutton of Lincoln University in the United Kingdom.

The team is now working on solving the mystery of how these larvae land safely. “We’re still just at the beginning in how the take-off works,” Sutton said, noting that this is the first adhesive latch found in these systems. It is hard to know how many other lift-generating latching systems there may be. Nevertheless, this new research is a leap forward in understanding and is already catching the attention of robotics and aeronautical engineers. (Journal of Experimental Biology)