A Rare Carnivorous Caterpillar That Wears The Remains Of Other Insects Has Been Found In Hawaii
In Hawaii, a rare carnivorous caterpillar was discovered to engage in a truly gruesome behavior. It disguises itself in the remains of other insects as it invades a spiderweb.
Then, it eats the spider’s dead or incapacitated catches. The caterpillar was aptly nicknamed the “bone collector” and has been scientifically described for the first time.
“I just couldn’t believe it. The first couple of times you find that, you think it’s got to be a one-off—it’s got to be a mistake,” said Daniel Rubinoff, the lead author of the study and an entomologist at the University of Hawaii at Manoa.
“I’ve been looking at it for over a decade, and it still blows my mind.”
Caterpillars are the larval stage of moths and butterflies, which are members of the Lepidoptera insect order. Most known Lepidoptera species are herbivores, but a small portion of them—0.1 percent—are meat-eaters.
The bone collector caterpillar is part of the Hyposmocoma genus, an ancient moth lineage that only exists in Hawaii.
Over two decades of field work, researchers have documented just 62 bone collector specimens. They have only been found on a single mountainside on the island of Oahu.
Hyposmocoma caterpillars spin silky casings around themselves for protection before transforming into moths. Other species usually attach pieces of shell, wood, and algae to their cocoons as camouflage, but the bone collector caterpillar prefers to use the remnants of dead insects it scavenges from around the spiderweb it lives near.
The researchers identified parts from six different insect families attached to the caterpillars’ cases, including weevil heads, beetle abdomens, and parts of a shed spider exoskeleton. They observed the caterpillars in action.
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In the lab, the caterpillars exclusively selected insect remains to add to their silk casings, ignoring other available natural pieces.
Sometimes, they chewed the body parts into smaller fragments. When two caterpillars were close by, they occasionally cannibalized each other.
It seems dangerous for a caterpillar to live right next to a spider since the arachnids are carnivorous as well. But the researchers have not come across any evidence of spiders eating the caterpillars.
“Hawaii is an isolated place, and the things that have gotten here have really thrown the rulebook out in terms of the ways they’ve evolved,” Rubinoff said.
However, the bone collector’s rarity makes it susceptible to the same environmental threats that many other Hawaiian insects face, such as habitat loss and invasive species.
According to the researchers’ analyses, the mysterious species is three million years older than the island of Oahu, which means it must have inhabited other regions at some point in time.
The details of the new study have been published in the journal Science.
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