6 Venomous Caterpillars That Look Cute—but Can Cause Painful Stings

Saddleback Caterpillar

For pure visual surprise, you almost can't top the colorful and almost comical appearance of the saddleback caterpillar (Acharia stimulea). "While it isn’t cuddly-looking, the bright green of its saddle is enticing—but this caterpillar shouldn't be picked up under any circumstances," says Emily Meineke, associate professor of urban landscape entomology at University of California, Davis. "It wants to be left alone and packs a sting from its hairs that will make anyone understand what an introvert it is."

Native to the eastern half of the United States, the saddleback's hairs can even leave venom behind. Despite the colorful appearance of the caterpillar, the adult moth is a nondescript brown.  

Monkey Slug Caterpillar

Like the saddleback, the monkey slug caterpillar (Phobetron pithecium) is native to the eastern United States. "The caterpillars are brownish and hairy in appearance and possess numerous tentacle-like structures," says Patrick Liesch, extension director at University of Wisconsin-Madison's Department of Entomology. "Skin contact can result in a burning, stinging sensation." They're also known as hag moth caterpillars.

The adult moths are small and brown, with adult males mimicking the appearance of a wasp and females mimicking the look of bees. 

White Flannel Moth Caterpillar

The adult white flannel moth is just as visually stunning as the caterpillar, with a solid white body and large antennae. The caterpillar, on the other hand, has a brown body with yellow polka dots.

"It's a good idea to avoid touching Norape ovina," says Meineke. "This cutie looks like it’s covered in soft tufts of hair, which it is, but underneath the tufts are shorter stinging hairs." It can be found mostly in the southeastern quarter of the United States.

Puss Caterpillar

Puss caterpillars (Megalopyge opercularis) look very soft, but don't be tempted to touch them. "These caterpillars are covered in fine, hair-like filaments and resemble an impressive hairdo more than a caterpillar," says Liesch. "However, they also have short spines that contain a potent chemical defense. If skin contact occurs, those spines can break off in the skin, leading to a burning and stinging sensation, followed by numbness, tingling, swelling, and nausea."

Out of all the caterpillars in the U.S., the puss caterpillar has the most painful and notable sting. "This species is mostly encountered in the south-central and southeastern United States," he adds.

Black-Waved Flannel Moth Caterpillar

The black-waved flannel moth caterpillar (Megalopyge crispata) looks quite wild—almost like it's having a bad hair day and static electricity issues. Its hairs are venomous and create burning and redness when they come in contact with skin. These caterpillars are light brown with a wing design that looks something like an old rug or blanket. 

Buck Moth Caterpillar

Bristly-looking caterpillars should usually be avoided, and the black and yellow buck moth caterpillar (Hemileuca maia) certainly falls into this group. These caterpillars have spines that are filled with venom and will cause a burning sensation when they touch your skin.