American Dagger Moth Caterpillar, Acronicta americana

As I was walking on the Little Miami Trail earlier this week, I saw this fuzzy yellow caterpillar with black tufts hustling across the pavement. I knew what it was right away--a young American Dagger Moth Caterpillar. The early instars of this caterpillar are bright yellow like this one, but the later instars get paler and paler, until they can be almost white. American Dagger Moth caterpillars are so fuzzy, cute and cuddly you just want to pick them up and let them crawl on you...but don't! I know this from experience. When Matty was about 2 years old, we were on the back deck when a big, beautiful white Dagger Moth caterpillar crawled in his path. He let the caterpillar climb up his arm and on his leg, and he was laughing...and loving the little thing, but I wasn't too keen on it, so I walked Matty to a tree and let the caterpillar climb onto a leaf. Good thing I did because wherever those fuzzy little hairs had touched his delicate baby skin a huge red welt appeared. I can't remember if the welts appeared within hours or the next day, but when I took him to the pediatrician, she knew right away what had happened to him. "Has Matty been playing with a fuzzy white or yellow caterpillar?" D'oh! When I got home, I looked up the caterpillar and learned all about him. A week later, an article appeared in the newspaper advising people to beware the cute, fuzzy white caterpillars roaming about. A week too late for us, but we always do tend to learn things the hard way...

A young American Dagger Moth Caterpillar (Acronicta americana) looking dapper in his bright yellow and black bristly hairs (setae).

...he is soft, he is fuzzy, but don't touch! Those silky looking hairs and tufts can leave stinging welts!

The American Dagger Moth caterpillar doesn't sting like a wasp or bee. It doesn't have a stinger at all. The fuzzy hairs (setae) are hollow, and when they touch the skin, they break away releasing toxins from poison glands to which they are attached. (Click here for details on "stinging" caterpillars.)

The toxin-wielding setae make me think of deadly little straws...like something out of James Bond...sort of. It's not like these caterpillars are "attack" caterpillars. They don't release their toxins on purpose. The toxins just spill out when the hair is broken.

...not all species of dagger moths have "stinging" setae or spines, but do you want to risk it? :-) Move along little caterpillar. Hope to see you again some day as a moth!