Meet the ‘Bone Collector’ Caterpillar That Wears Its Victims

The animal kingdom can be creepier than a Stephen King novel sometimes, and a newly discovered creature proves this is true. Researchers called this new insect a “bone collector” — are you scared yet? You don’t have to be! It might sound like something out of a horror movie, but a bone collector is just a caterpillar with a really unique way of capturing prey.

This caterpillar, which belongs to the Hyposmocoma genus, is a carnivorous and cannibalistic insect. But the most goosebump-inducing part is that the caterpillar will actually cover itself in the body parts of dead insects, according to an article published in Science. (*shudder!*) The researchers say this bone-collecting caterpillar is only found in a small area on an O’ahu mountainside, and its evolutionary lineage dates back at least six million years.

How It Hunts for Prey

Although most caterpillars are herbivores (less than 0.13% of the almost 200,000 species of moths and butterflies are predatory caterpillars!), the bone collector does eat other insects. It will first find an enclosed spider web, such as one under tree bark, and then grab leftover pieces of the spider’s dinner to make itself a covering of inedible insect parts, bound together with silk. It will also feed on the unlucky insects the spider has caught.

Scientists have observed caterpillars behaving this way prior to the April 2025 study published in Science, led by entomologist Daniel Rubinoff of the University of Hawaiʻi at Mānoa. However, experts couldn’t find evidence that it was a unique species, as, until now, only 62 individual caterpillars exhibiting bone collector behavior had been found in 20 years, per Science Alert. However, this discovery shows that the bone collector caterpillar is its own unique species, which is already considered endangered due to its rarity and limited range.

“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,” Rubinoff said about this discovery, per Scientific American. “I’ve been looking at it for over a decade, and it still blows my mind.”

It’s also kind of gross. This is not a cute caterpillar you see in a children’s book or let crawl around your arm at a picnic. This caterpillar means business, and even Rubinoff admits it’s a little icky. “It’s gross at one level, but it’s also kind of adorable,” he told 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.’”

They Lay Eggs in Spiderwebs

When bone collector caterpillars mature, they turn into moths and leave behind their creepy, bone-wearing habit. However, they pass it on to their offspring by laying eggs in a spiderweb. From there, the newly hatched caterpillar collects bones to “camouflage itself from the spider landlord,” according to Rubinoff. He said, “The only chance they have of making a living in this situation is to decorate or die; they live for fashion.”

Apparently, when bone collectors have their coats on, they can blend in with a spider’s environment by both appearance and smell. This is likely a defense mechanism to protect the caterpillar from being eaten by the spider it is stealing from.

When researchers studied bone collectors in a lab environment, they found that the caterpillars didn’t even attempt to create a disguise from bits of twig or leaf, or bark; only insect parts. In the controlled environment of the study, the bone collectors would eat other insects and even each other, possibly to eliminate food competition (although this doesn’t bode well for the future of this species).

Although the bone collectors steal food from spiders, they are not considered parasitic or symbiotic with spiders. Instead, they are considered scavengers, mostly picking from meals the spider has already finished and sometimes eating each other.

Hawaiian Caterpillars

Akito Kawahara, director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum, who was not involved in this research, told Scientific American that bone collectors have “adapted to the environment because the conditions of Hawaii are very different from other places around the world.” He added, “Insects do everything. They’re amazing. In some ways, I was not surprised [by the bone collectors] because I know insects do some really crazy things.”

The bone collector is part of the Hyposmocoma genus, which is native to Hawaii and includes over 350 described species, many of which are found in a single valley or volcano within a Hawaiian island. One Hyposmocoma caterpillar on Maui is the only snail-eating caterpillar. There are also aquatic caterpillars, which act the same on land or underwater, and are the only example of amphibious insects. Many of the Hyposmocoma caterpillars are known for spinning portable silk cases to hide in, but this is the first caterpillar to use insect remains. It’s just another example of how incredible the creatures we share this planet with are!

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