On a single mountain range on the Hawaiian island of Oʻahu, scientists have identified a species of carnivorous caterpillar with a macabre lifestyle: it lives in cobwebs and feasts on weakened or dead insects, then decorates itself in the remains of its prey.
The “bone collector” caterpillar’s behavior has not been seen in any other species of butterfly or moth (order Lepidoptera). In a new article in the journal Science, researchers from the University of Hawaiʻi at Mānoa report that the caterpillar, the larva of a moth in the genus Hyposmocoma, doesn’t just stick insect body parts to itself; it also adjusts the parts before attaching them to its outer case. If the chunk is too large, the larva chews it down to size. And the caterpillar isn’t picky regarding the type of deceased insect it choose as ornaments. The researchers found body parts of weevils, flies, bark beetles, spiders, and ants attached to the cases.
The “bone collectors” co-habit in cobwebs with the resident spiders, another never-before-seen act in any caterpillar species, and may use the body parts to camouflage themselves from their arachnid landlords. The researchers note that they never observed any spider-gnawed larvae or any wrapped in spider silk. In addition, caterpillars wandered the webs of at least four spider species not native to Hawaii, suggesting that the larvae had adapted to the invasive spiders’ presence.
Over 22 years of fieldwork on “bone collector” caterpillars, the researchers found only 62 specimens within a range of 15 square kilometers (5.79 square miles) of forest in O’ahu’s Waiʻanae mountain range. Scientists fear that the species’ population may be unstable and, like other endemic Hawaiian fauna, threatened by introduced predators. Without conservation efforts, the “bone collector” caterpillar will likely disappear.
Meat-eating caterpillars are extremely rare. Less than 1 percent of species in Lepidoptera are carnivorous, making the discovery of this species and the need to protect it especially urgent.
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