Meet the bone collectors. These frighteningly named caterpillars cover themselves in bug body parts! They’re the larvae of a newly discovered moth species found in just one mountain range on the island of Oahu, Hawaii. The caterpillars’ grisly habit of encasing themselves in corpses is actually a clever adaptation to help them survive.
Bone collector caterpillars live near spider-webs, from which they scavenge the spiders’ prey. “It’s a dangerous occupation,” says Daniel Rubinoff, an entomologist—or scientist who studies insects—at the University of Hawaii at Manoa. Normally, spiders see juicy caterpillars as delicious snacks. But the eight-legged predators ignore the disguised bone collectors.
The caterpillars create costumes by attaching a variety of dead bug bits—like heads, wings, legs, and even shed spider skins—to a sticky silk case they spin around themselves. These body parts make the caterpillars look like unappetizing piles of discarded carcasses. The trick allows bone collectors to live near spiders without being eaten! The caterpillars also get easy access to trapped prey and spiders’ leftovers, like half-eaten flies, beetles, and ants. Meat-eating caterpillars are extremely rare: Only about 1 in 800 caterpillar species are carnivorous, says Rubinoff.
Bone collectors belong to the genus Hyposmocoma, which contains more than 400 moth species. All their larvae wear decorated silk cases—though none are as creepily adorned as bone collector caterpillars. The other caterpillars instead choose to don bits of wood, algae, lichens, or gravel.