Hawaiian caterpillar patrols spiderwebs camouflaged in insect prey's body parts.

Abstract

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 spider's webs, feeding on the arthropods that they find there. This Hawaiian lineage also boasts an unprecedented and macabre practice of decorating its portable larval home with the body parts of the spider prey it harvests from the web where it resides. Phylogenomic data suggest that the origin of this unique spider cohabitant is at least six million years old, more than one million years older than Hawaii's current high islands. After decades of searching, only one species has been discovered, and it is restricted to 15 square kilometers of a single mountain range on the island of O'ahu, meaning that other members of the lineage have disappeared from older islands. Conservation action to save this globally unique lineage is imperative and overdue.