Scientists find previously unknown jumping behavior in insects

A team of researchers has discovered a jumping behavior that is entirely new to insect larvae, and there is evidence that it occurs in a range of species – we just haven’t noticed it before.

The previously unrecorded behavior occurs in the larvae of a species of fed flat bark beetle (Laemophloeus biguttatus). Specifically, the larvae can jump into the air, with each larva curling itself into a loop as it leaps forward. What makes these jumps unique is how the larvae do it.

“Jumping is extremely rare in the larvae of beetle species, and the mechanism they use to perform their jumps has not been previously recorded in insect larvae as far as we can tell,” said Matt Bertone, corresponding author of an article on the discovery and director of the Plant Disease and Insect Clinic at North Carolina State University.

While there are other insect species capable of miraculous jumps, they rely on something called a “latch-mediated spring actuation mechanism.” This means that they essentially make two parts of their bodies snap together as the insect exerts force and builds up a significant amount of energy. The insect then unlocks the two parts, releasing all that energy at once, allowing it to jump off the ground.

“What makes the L. biguttatus so remarkable is that it makes these jumps without clicking two parts of its body together,” says Bertone. “Instead, it uses claws on its paws to grip the ground as it builds up that potential energy — and once those claws release their grip on the ground, that potential energy is converted into kinetic energy, launching it toward the sky.” .”

The discovery of the behavior was somewhat accidental. Bertone had collected a variety of insect samples from a decaying tree near his lab to photograph them when he noticed these beetle larvae appeared to be jumping.

Bertone and paper co-author Adrian Smith then decided to film the behavior to better see what was going on. Then they began to understand how peculiar the behavior was. Smith is a research assistant professor of biological sciences at NC State and chief of the Evolutionary Biology & Behavior Research Lab at the North Carolina Museum of Natural Sciences.

“The way these larvae jumped was impressive at first, but we didn’t immediately understand how unique it was,” says Bertone. “We then shared it with a number of beetle experts across the country, and none of them had seen the jumping behavior before. Then we realized we needed to take a closer look at how the larvae were doing exactly what they were doing.”

To determine how: L. biguttatus could perform his acrobatics, the researchers filmed the jumps at speeds of up to 60,000 frames per second. This allowed them to capture any external movements associated with the jumps, suggesting that the legs essentially formed a locking mechanism with the ground.

The researchers also performed a muscle mass assessment to determine whether it was possible for the larvae to make their jumps using only their muscles, rather than using a locking mechanism to store energy. They found that the larvae didn’t have enough muscle to hurl themselves into the air as far or as fast as they were filmed jumping. Ergo, clinging to the ground was the only way the larvae could deliver their aerial performance.

Meanwhile, in an unrelated video about jumping maggots, Smith had included a short clip of the jumping behavior in L. biguttatus. That video was seen by a researcher in Japan named Takahiro Yoshida, who had witnessed similar jumps in the larvae of another beetle species called Placonotus testaceus, but had not published anything about the behavior.

“We don’t have high-speed footage of P. testaceus, but the video evidence we have from Yoshida’s lab suggests that this previously unknown behavior is found in two different sexes that aren’t even closely related,” Bertone says.

“This raises many questions. Did this behavior evolve separately? Does it occur in other beetle species? Are these genera more closely related than we previously suspected? There is a lot of interesting work to do here.”

Video of the jumping behavior in L. biguttatus can be found at https://www.youtube.com/watch?v=y-b73G96UIQ.

The article, “A Novel Power-Amplified Jumping Behavior in Larval Beetles (Coleoptera: Laemophloeidae)”, is published open access in the journal PLOS ONE. The article was co-authored by Yoshida, of Tokyo Metropolitan University; Joshua Gibson, of the University of Illinois at Urbana-Champaign; and Ainsley Seago, of the Carnegie Museum of Natural History. The work was done with partial support from the Japan Society for the Promotion of Science for Young Scientists.

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Note for editors: The study summary follows.

“A New More Vigorous Jumping Behavior in Larval Beetles (Coleoptera: Laemophloeidae)”

authors: Matthew A. Bertone, North Carolina State University; Joshua C. Gibson, University of Illinois at Urbana-Champaign; Ainsley E. Seago, Carnegie Museum of Natural History; Takahiro Yoshida, Tokyo Metropolitan University; and Adrian A. Smith, North Carolina State University and the North Carolina Museum of Natural Sciences

published: 19 Jan. PLOS ONE

Abstract: Larval insects use many methods of locomotion. Here we describe a previously unknown jumping behavior in a group of beetle larvae (Coleoptera: Laemophloeidae). We analyze and describe this behavior in Laemophloeus biguttatus and provide information on similar observations for another Laemophloid species, Placonotus testaceus. Laemophloeus biguttatus larvae precede jumps by bending their bodies while grasping the substrate with their legs for a period of 0.22 ± 0.17 s. This is followed by a rapid ventral curl of the body after the larvae release its grip which launches them into the air. Larvae reached take-off speeds of 0.47 ± 0.15 m s-1 and traveled 11.2 ± 2.8 mm (1.98 ± 0.8 body length) horizontally and 7.9 ± 4.3 mm (1.5 ± 0.9 body length) vertically during their jumps. Conservative estimates of power delivered revealed that some, but not all, jumps can be explained by direct muscle power alone, suggesting: Laemophloeus biguttatus may use a latch-mediated spring mechanism (LaMSA) in which interaction between the larvae’s legs and the substrate serves as a latch. MicroCT scans and SEM imaging of larvae revealed no notable changes that would aid in jumping. While more in-depth experiments could not be performed to test hypotheses about the function of these jumps, we argue that this behavior is used for rapid locomotion, which is energetically more efficient than crawling the same distance to spread out of their ephemeral habitat. We also summarize and discuss jumping behavior in insect larvae for additional context of this behavior in laemophloid beetles.

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