I hereby apologize to all venomous caterpillars for comparing them to Donald Trump.
They are genuinely fascinating and/or beautiful and enticing and I meant no slander.
Southern flannel moth - Megalopyge opercularis
Also known as the “puss moth” or “tree asp” (for its luxurious-looking “fur” and its extremely painful sting, respectively), Megalopyge opercularis is a deceptively cute tribble of a caterpillar found in the Eastern and Southern United States. It’s most common in Texas, but can be found along the Eastern Seaboard as far north as New Jersey.
Both the adult and juvenile forms of M. opercularis have urticating (itch-inducing) hairs on their body, much like some other caterpillar species, but the asp takes it one step further, and has clusters of venom-filled spines under its hairs.
As they most often live in popular shade trees, caterpillars occasionally lose their grip and tumble down onto unsuspecting humans just trying to have a nice day at the park. Their reproductive cycle means they’re particularly abundant in late spring/early summer and mid autumn. The sharp spines pierce the skin and automatically inject venom for as long as they’re embedded in the skin. Unlike with snakes, the caterpillars have no control over whether or not the venom is used.
Despite their relative abundance, especially in Texas and Louisiana, many doctors and first responders wouldn’t know the signs of an asp encounter if it crawled out of Donald Trump’s (clearly asp-inspired) toupee and stung them on the nose.
Most patients (but not all) experience extreme pain at the location of the sting, and that pain often radiates to the nearest lymph nodes. Swelling occurs at the sting in a raised halo, which then recedes to show the pattern of the spines on the caterpillar (lower image). While the pain rarely lasts longer than 48 hours, some patients may experience lymphadenitis (swelling of the lymph nodes) for up to a week.
So what do you do if you’re unfortunate enough to directly encounter a tree asp?
Step 1: Cellotape! Or scotch tape, whatever you call it. Take a strip of it, put it over where the asp landed/got squished/you had the bad idea to pick it up. Remove it. Repeat several times. This helps get out any spines (which can be near-invisible) stuck in the skin. Protip: This is also useful if you ever fall into a cactus. Believe me. I’d know.
Step 2: If the pain is super intense, see a doctor. Bring with them any information about the bug that you can, but maybe don’t bring the actual caterpillar unless you have a way of handling it without getting stung again. If it’s just really bad (no, seriously, these things can bring grown men to their knees), take some anti-inflammatory drugs (such as ibuprofen or tylenol), some anti-histamines, or both.
Step 3: Wait. Sorry bud, this next day or two is gonna suck. Ice the area if you want, to numb it up. Have a beer. Eat some ice cream. Watch a movie. Try not to think about it.
If you have any trouble breathing or seeing or any other serious symptoms go directly to the emergency room. Tell them what stung you. They might not know what to do off the top of their head, but they have resources!
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Images:
The Puss Caterpillar and the Effects of its Sting on Man, USDA Circular 228. F. C. Bishopp, September 1923.