Montana Public Radio

Bug Bytes: Carnivorous Caterpillars

Jun 12, 2020

With nearly 180,000 species of moths and butterflies in the world, it goes without saying that their larval stage of development – caterpillars – are equally abundant. And of all the different types of caterpillars in the world, inchworms are perhaps the best-known group.

Inchworms are species of moths in the family geometridae. Most of us have seen cute little inchworms inching along a branch or dangling from the tree canopy on a strand of silk. Their bodies tend to be green, brown or tan in color, helping these small caterpillars blend into their surroundings. With soft, almost gummy-like bodies, they’re seen as gentle vegetarians that have been the focus of many children’s books and stories.

That is, except for the ferocious gang of inchworms found in Hawaii.

Of the 23,000 species of geometrid moth caterpillars in the world, about 20 from a specific genus in Hawaii are hardcore predators. Rather than munching on leaves, these little terrors use their camouflage to resemble a twig, stem, or leaf lying in wait.

A non-carnivorous horned spanworm moth caterpillar.
Credit Glenn Marangelo

When a potential meal is in range, they strike quickly, using six sharp, pincer-like daggers on the end of their legs to capture their prey. On the menu are flies, crickets, cockroaches…even other caterpillars and adult moths.

Caterpillars in this genus can be found around the world, but are vegetarian elsewhere. As to why these Hawaiian caterpillars developed a hunger for meat rather than plant material is a mystery…but the lack of other insect predators is a likely contributor.

So, the next time you see a cute little inchworm happily munching a leaf, pause to think about its ferocious relatives in Hawaii that break the mold in terms of expected caterpillar behavior.

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