Creepy camouflage artists: Bone-collecting caterpillar builds itself a dress from prey remains

Honolulu. In a horror film, the carnivorous bone-collecting caterpillar would be a terrifying figure without scruples: The newly discovered species creates a carefully crafted cloak of camouflage from the inedible body parts of its insect prey. Researchers report on this equally gruesome and fascinating observation in the journal Science.

The scientists discovered the bizarre insect larvae in a small, 15-square-kilometer patch of mountain forest on the Hawaiian island of O'ahu. Not only do the caterpillars inhabit a small area, they are also very rare: after years of searching, only 62 specimens have been observed.

The bone-picking caterpillar uses body parts of its prey insects as camouflage. The image shows various variations of this carefully constructed camouflage.

Source: Rubinoff Lab, Entomology Section

According to the scientists, the fact that the extraordinary new species was discovered in Hawaii is no coincidence: The geographical isolation of the archipelago has given rise to a whole range of bizarre species, including dragonfly larvae that live on land rather than in water, spiders that impale their prey from the air, and a whole range of carnivorous caterpillars. Such carnivorous caterpillars are a rarity in themselves: Of the nearly 200,000 currently known moth and butterfly species, just 0.1 percent of the larvae exhibit such predatory behavior.

Even more unusual, however, is the hunting behavior of the bone-picking caterpillar: This insect, which belongs to the moth genus Hyposmocoma, which is found only in Hawaii, lives exclusively in spider webs woven in tree hollows or rock crevices. The caterpillars crawl through these webs, stalking weakened or recently dead insects that have become entangled in the web. They don't even stop at other members of their own species, cannibalizing them if they encounter a smaller specimen.

What is remarkable, however, is what the caterpillars decorate themselves with in order to avoid being discovered by their spider host: For example, they wear inedible body parts of their prey as camouflage, write the three scientists: "The body parts are carefully measured for size before the caterpillar weaves them into its collection." Each potential new addition is turned several times, felt with the mouthparts, and mostly chewed down to a size that fits into the shell.

The strategy seems to be working: so far, they have not observed any bone-collecting caterpillars killed or caught by spiders, the study says.

RND/dpa