Researchers Discover a Rare, Carnivorous Caterpillar That Wears Dead Insect Parts to Fool Spiders The species, dubbed the “bone collector,” belongs to an ancient lineage of moths older than the Hawaiian island of Oahu, which is the only place it’s known to live today A "bone collector" caterpillar sits in a cobweb with a spider and its egg sac. The newly discovered moth species disguises itself as a larva by covering itself with insect parts. Daniel Rubinoff Researchers in Hawaii have discovered a rare, carnivorous caterpillar with a gruesomely unique behavior: It camouflages itself in insect remains as it trespasses into a spiderweb—then it eats the spider’s weakened or dead catch. Appropriately nicknamed the “bone collector,” the caterpillar has been described for the first time in a study published Thursday in the journal Science. “I just couldn’t believe it. The first couple of times you find that, you think it’s got to be a one-off—it’s got to be a mistake,” Daniel Rubinoff, lead study author and an entomologist at University of Hawaii at Manoa, tells Scientific American’s Gayoung Lee. “I’ve been looking at it for over a decade, and it still blows my mind.” “It’s a great piece of field work,” evolutionary biologist David Lohman from the City College of New York, who did not participate in the study, says to National Geographic’s Carolyn Wilke. A museum specimen of an adult female bone collector moth that was reared in the Rubinoff lab Daniel Rubinoff Caterpillars are the larval stage of butterflies or moths, which are members of the Lepidoptera insect order. While the majority of known Lepidoptera species are herbivores, a miniscule 0.1 percent of them are meat-eating, according to a statement. Specifically, the bone collector caterpillar is part of the genus Hyposmocoma, an ancient lineage of moths that only exists in Hawaii. As if that wasn’t unusual enough, in 20 years of field work, researchers have documented just 62 bone collector specimens—and they’ve only been spotted on a single mountainside on the island of Oahu. Beyond these exceptional traits, “what’s incredible about it is its behavior,” says Rubinoff to Popular Science’s Lauren Leffer. Hyposmocoma caterpillars spin silky, protective cases around themselves, which they carry before transforming into moths. While other species typically attach pieces of shells, wood and algae to the case as a camouflage, the bone collector caterpillar goes for a more eccentric look: bits of dead insects it scavenges from around its host spiderweb. These six bone collector caterpillar specimens adorned their cases with beetle wings, ant heads, fly wings and legs, spider legs and other insect body parts. Their cases—the gray material seen through the detritus—are made from caterpillar saliva and silk. Daniel Rubinoff Rubinoff tells the New York Times’ Jack Tamisiea that the “behavior was utterly unknown.” He and his colleagues identified parts from six different insect families attached to the caterpillars’ cases, including beetle abdomens, weevil heads and parts of a shed spider exoskeleton. “It’s gross at one level, but it’s also kind of adorable,” he adds to National Geographic. “They’re cruising around like, ‘Oh, this looks delicious. I’ll eat some of this and then put the rest on my back.’” Researchers observed the bone collectors closely inspecting their scavenged goods—in the lab, the caterpillars would select only insect parts to adorn their silk cases, ignoring other natural pieces that were available. Sometimes, the larvae would chew these body parts into more desirable sizes. And when two caterpillars were in proximity, they occasionally cannibalized each other. Bone collector caterpillar Watch on Living alongside a spider is not an intuitive life choice for a caterpillar, given that spiders are also carnivorous. “It’s like they’re literally living in the lion’s den,” Rubinoff tells Gizmodo’s Ed Cara. But researchers haven’t found any evidence of spiders eating the bone collectors, so something must be working for them. “Hawaii is an isolated place, and the things that have gotten here have really thrown the rulebook out in terms of the ways they’ve evolved,” he adds. However, the bone collector’s isolation and rarity makes it vulnerable to the same environmental pressures that threaten many Hawaiian insects, such as invasive species and habitat loss, according to the statement. In fact, the researchers’ analyses indicate the mysterious species is three million years older than the island of Oahu, suggesting it once inhabited other regions. “There is really a concern that we need to do better with conservation,” Rubinoff tells the Associated Press’ Adithi Ramakrishnan. Get the latest stories in your inbox every weekday.