The carnivorous “bone collector” caterpillar is the only known species of its kind, researchers say, and its ancient lineage may soon die out.

Researchers from the University of Hawaii at Manoa detailed their discovery in a paper published Thursday in Science. The caterpillar—which they’ve dubbed the “bone collector”—uses the disguise to live hidden within a spider’s web, where it can prey upon other small bugs that get stuck inside. Unfortunately, the unique caterpillar’s continued survival is likely under threat, since it’s only known to exist on a single mountain range on one Hawaiian island.