The vast majority of lepidopteran caterpillars are herbivorous. Those that break this rule tend to do so in unexpected ways, such as the Hawaiian inchworm, an ambush predator. Rubinoff et al. describe another unusual caterpillar, also from Hawaii, that scavenges discarded insect parts. The “bone collector” lives in spider webs and feeds on the discarded bits of the spider’s insect prey. Perhaps to avoid detection, these caterpillars construct portable cocoons decorated with inedible discarded parts. This species is 5 million years older than the oldest Hawaiian island, but is now highly endangered, being found in only a single population on Oʻahu.⁠ ⁠ ⁠ _____⁠ ⁠ Lepidoptera is the most herbivorous of all the insect orders, with predatory caterpillars globally comprising less than 0.13% of the nearly 200,000 moth and butterfly species. Here, we report a species in which caterpillars are carnivorous inhabitants of spiders’ webs, feeding on the arthropods that they find there. This Hawaiia...