Never touch anything that looks like Donald Trump’s hair.

~Gwen Pearson

Puss Caterpillar, or is it? (click photos to enlarge)

I just love that quote. It is the title of an article in WIRED last week on a particularly painful caterpillar known by various names – Puss Caterpillar, Asp, and Southern Flannel Moth Caterpillar, Megalopyge opercularis. I find one of these every couple of years as I wander the woods and fields, especially in early September in preparation for the NC Museum of Natural Sciences’ biggest special event, BugFest. Years ago, I started a caterpillar tent at BugFest as a way to share my passion for all things caterpillar and now I volunteer at the event. People really do love to look at (and learn about) caterpillars. Most of the larvae are fun to raise, identify, and are totally harmless. But, there are a few that can inflict pain when touched. They have “urticating hairs” that contain venom. And this one is supposedly the most painful of all.

Next to last instar of Puss Caterpillar

I found one last week on a Red Maple. This species feeds on a variety of tree leaves, which fortunately makes it less likely someone will accidentally encounter one unless it falls out on you or you are climbing up there amongst them. This one looked a little different than most I have found, especially in its more strawberry-blonde coloration. But there was something else I couldn’t quite peg. I found an incredible online resource on these moths and their larvae that helped me see the reason (see http://entnemdept.ufl.edu/Creatures/MISC/MOTHS/puss.htm). Turns out, the color can vary from grayish-brown to tan. The big thing I learned was about the different looks of this caterpillar as it goes through its various molts (instars). The caterpillar had become still a couple of days ago and made a silken pad for itself on a leaf. This is usually a sign of impending change, a molt. After reading more about it and seeing pictures of the last two instars of these larvae, I went out to look at my Puss Caterpillar again.

Puss Caterpillar, last instar

It had molted and, did indeed, look different, more like the pictures you usually see in field guides (most guides use an image of the caterpillars in their last instar as the key for identification). The color was slightly darker, with more tints of gray. It had some noticeable tufts on each side, tipped in white. And the whole effect was as if someone had given the furry little guy a good combing and maybe put some mousse in to tidy up the hairs, especially along the dorsal crest and “tail”. I looked for the shed, but, as the reference stated, most usually eat their shed skin, and it appears mine followed suit.

Top view of next to last instar

Top view of last instar

While transferring the caterpillar back into its cage, I did what I really did not want to do – I accidentally touched it. Just a glancing brush, with my knuckle. I immediately pulled away and said a few choice words, expecting the worst. I have been “stung” by a few other species in the past, and most felt like a wasp sting, the pain usually dissipating in a few minutes. This one started out with a mild stinging sensation, but then seemed to move deeper. Soon, it felt as if my knuckle bones had been shot with some painful solution. Luckily, I had apparently just barely touched it, so the pain did not spread as I have read it often does. The knuckle soreness lasted several hours and then finally faded. I made a promise to myself to be extra careful when anywhere near these little “fur balls”. There is a lot of good information on the referenced site, so rather than repeating it all here, I refer you to the Featured Creatures page on this species from the University of Florida. If you want to see this, other cool caterpillars, and lots of interesting displays on all things arthropod-ish, be sure to come to BugFest at the NC Museum of Natural Sciences in downtown Raleigh this Saturday, September 20. And remember, if you see something that looks like a crawling eyebrow or that rich guy’s windblown coiffure, don’t pet it.