With nine wiggly appendages, hairy body and suction cup feet, the larval stage of the hag moth is so unique it looks like a tiny extra from a science fiction movie.

In reality, it’s one of the more common caterpillars in Maine, but it’s rare to spot one. That’s because it spends most of its time feeding on the undersides of leaves and can be mistaken for a spider.

The monkey slug is a member of the slug caterpillar moth family. These are caterpillars that instead of tiny legs, have suckers. So when in motion, monkey slugs look like they are gliding instead of crawling.

The monkey slug got its name because it has dense, brown hair-like structures on its body that look like fur and appear monkey-like.

“They are a funny one,” said Jim Dill, pest management specialist at University of Maine Cooperative Extension. “It’s one of those things that’s really common, but also rare.”

The monkey slug has a wide distribution throughout New England and into Maine. But few people ever see one, Dill said, because the caterpillar’s brown coloration allows it to blend in with leaves and dirt.

Cody Pooler was not exactly sure what he was seeing when he spotted one in Dexter recently.

“I thought the creature was pretty gnarly and didn’t know what to think of it,” Pooler said. “My boys thought it was an alien or baby alien.”

Pooler said his first thought was they had encountered a baby octopus, but he quickly discounted that since Dexter is far from the nearest ocean.

The monkey slug caterpillar is a common one in Maine, though rarely seen. It resembles a terrestrial octopus or a space small alien. Credit: Courtesy of Griffin Dill

“They are not commonly encountered,” Dill said. “I get one call a year about them if I am lucky.”

The monkey slug’s most distinctive characteristic are nine appendages extending all around its body. According to Dill, those appendages are equal parts defensive and ornamental.

“The interesting thing is the caterpillar is really a thin body in the middle of those wiggly things,” Dill said. “Those appendages can break off and not hurt the critter at all.”

Those appendages are an adaptation that make the monkey slug look bigger than it actually is and could frighten off enemies, Dill said. That they break off easily could startle a predator enough that the monkey slug could escape.

They are also covered with stinging hairs.

“Take all of that together and you have a camouflaged, stinging, breakaway type of critter,” Dill said.

Monkey slugs are not destructive and feed on a variety of trees and shrubs. The female hag moth lays her eggs one or two at a time over a wide area, so when the larvae emerge, they are scattered over that large area.

“If you happen to see one, you’d be hard pressed to find another one nearby,” Dill said.

Unlike the caterpillar stage, the adult stage of the hag moth is fairly nondescript. It has a greyish-black body with little white tufts on either side.

Those hair-like structures on the monkey slug do contain toxins, but Dill said they don’t present the same danger to humans as the hairs on the browntail moth caterpillars.

“If a monkey slug got on you and you swatted it or scrunched it, you could get a reaction and a rash,” Dill said.

Monkey slug hairs also don’t remain in the environment like browntail moth caterpillar hairs, which remain toxic long after they are shed.

Pooler said he and his boys were thrilled to come across something so unique.

“I’m glad folks enjoy the amount of nature there is,” Pooler said. “And glad we were able to come in contact with a creature that’s very minimally seen and something so strange and out of the ordinary.”

Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.