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Fluffy bunny lost its tail? No, just a caterpillar that packs a punch!

Nantucket has one of the most toxic caterpillars in North America

Cute and fuzzy, but do not cuddle!

First instar of the puss moth caterpillar
Later stage puss moth caterpillar (photo curtesy of
The adult no longer has the stinging hairs. Hooray!

Back in 2005 when I was a field assistant with the Nantucket Conservation Foundation, I spent many days in the heathlands on my hands and knees counting vegetation. One early fall day as I placed my hand on the ground a severe pain, generating from the palm of my hand, pulsed up through my arm. Looking back at the spot where my hand had been I expected to see a shard of glass, a giant thorn, or a wasps nest. None of the above. I had just squished a puss moth caterpillar with the palm of my hand.

Puss moth caterpillars, or flannel moths (Megalopygidae family), are described as one of the most toxic caterpillars in North America. They appear soft and harmless, often described as wispy cotton or fur balls on leaves. Despite this innocuous appearance, they can pack a punch. According to Caterpillars of Eastern North America, by David Wagner, beneath the soft outer hair are hollow, poison-filled stinging spines that can deliver a pretty painful sting. When the caterpillar rubs or presses against skin, the venomous spines can become embedded.

These caterpillars are more often found in the North American south, but there are three species found farther north. On Nantucket we have Megalopyge crispata, often found in the heathlands and shrublands of the outwash plain. They feed on a number of plants, but I’ve seen them most frequently on black huckleberry (Gaylussacia baccata) and bayberry (Morella caroliniensis). This time of year they appear as white cotton balls. Later, as they consume more vegetation, they will grow darker and less wispy resembling a tiny tribble. Because of this cuteness factor, it would be wise to advise children about them so they do not pick them up.

Reaction stings can be severe, but the majority of people will only feel an irritation akin to a bee sting lasting about an hour. However, stings can cause throbbing pain, burning, and a rash. According to the Merck Manual medical reference, more susceptible patients can experience swelling, nausea, abdominal pain, headache, shock, and even respiratory distress. In his book, Wagner describes working with specimens in his caterpillar collection and inhaling some of the stinging hairs. The irritation, burning, and swelling escalated to a point where he checked himself in to the local hospital. After an hour or so, the symptoms subsided and he was free to go.

As for me back in 2005? With numbness and swelling travelling up my arm, I was rushed to the hospital by my co-workers. Apparently, I am not only sensitive to the stings, but by squishing it with my palm, I had the full amount of toxin delivered to one of the most sensitive spots on the body. The staff at the Nantucket Cottage Hospital had never heard of puss moth caterpillars. They thought it must have been a bee or wasp sting despite my protests. Two Benadryl and a few hours of sleep later, I was good as new.

So, what should you do if stung by a puss moth caterpillar?

  • Wash the skin with soap and water
  • Use local cooling like an ice pack to reduce pain and swelling
  • Rub the area with an alcohol swab
  • Putting tape on the site and then ripping it off can remove the embedded hairs

Well, puss caterpillars may be one of the most toxic, but they still have nothing on ticks.