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These Small Animals Wiggle As One—Here's Why

Video shows how sawfly larvae react in unison when faced with a threat.

This Bug's Form of Defense? Synchronized Wiggling This group of sawfly larvae banded together as a strange but effective method of defense.

Young sawflies are remarkably in sync. During their larval stage, they do everything together from fending off predators to traveling in one, cohesive pile.

And when these youngsters are approached by a potential threat, they often rise up, wiggling in unison. Baby sawflies look much like caterpillars, and they’re soft and vulnerable to being eaten. However, when banded together, they stand a greater chance of survival.

“[It] reminds me of a cohesive group of Spartan warriors,” National Geographic grantee Aaron Pomerantz, an entomologist, said in his original tweet showing the sawflies. Pomerantz has been conducting research in Tambopata, Peru, a town in the Amazon rainforest, for several years. It was the first time he had seen the bizarre phenomenon in person.

From afar, the group of larvae looked like a flower perched on the side of a tree, but closer inspection revealed it to be a cluster of wiggling worms. Not wanting to let his discovery go undocumented, he took video that shows the small, caterpillar-like larvae at rest on the side of a tree trunk.

When Pomerantz moved his hand closer to the cluster, the sawflies stiffened and bent upward in unison before plopping back down. The sawfly larvae were most startled when he breathed on them or placed his hand on the trunk of the tree, he explained in an email to National Geographic.

“Perhaps this ‘wave’ response and head-banging is a way to look like a larger organism to a would-be predator, such as a bird, which would have no problem picking off an individual sawfly,” he said.

Depending on the species of sawfly, they’ll stay in this larval stage for about a month before they drop to the ground and pupate, turning into a flying adult that looks similar to a wasp. Until then, the young stay in a group.

Group movement isn’t just useful for warding off predators. Sawfly larvae have also been seen traveling together, moving their tiny feet in unison to create a synchronously oozing motion.

Scientists have studied how working together increases sawflies’ chances for survival, and found that those chances may not be equal for all. Leaders and followers naturally emerge from the group, and in the steel-blue sawfly, leaders had a slight advantage in avoiding predators and accessing nutrients, researchers reported in 2014 in the journal Proceedings of the Royal Society B.

Not much is known about how sawflies coordinate their actions, but research from Western California University found that they can communicate via vibrational cues. Individuals of one species in Australia foraged for food alone at night but rejoined the group by tapping vibrations on tree trunks.

For Pomerantz, seeing the cluster of sawflies was a testament not only to the rainforest’s incredible diversity, but also to the thousands of species of sawflies exists than can be seen throughout the world.