You Can Look, But You’d Better Not Touch

It may appear cute, fuzzy, and pettable, but this pile of fluff attached to a grass blade at the Sandylands Sanctuary in East Texas is best avoided. A larval stage of the Black-Waved Flannel Moth (Megalopyge crispata), its hollow hairs contain toxins designed to protect the caterpillar from predators.

When other creatures — including humans — brush against the hairs, they break away and release the toxin, producing a painful rash or sting. Depending on the species and a person’s sensitivity, swelling and inflammation, numbness, or even fever and nausea might result.

The view from below


While younger Black-waved flannel moth larvae sport long, white wispy hairs, in their final larval stage they look very much like the best known stinging caterpillar in Texas: the Southern Flannel moth (Megalopyge opercularis). Commonly known as puss moths, or ‘asps,’ they can be abundant in live oak,  pecan, elm, and hackberry trees, as well as in yaupon and other shrubs.

Occasionally, they’ll drop from the trees onto cars or pavement below. When I found one on my car yesterday, it served as a timely reminder that their season has arrived.

The also-cute-but-dangerous Texas asp

Venomous hairs hidden beneath the silky outer hairs of the asp can deliver a sting even more painful than that of the Black-Waved flannel moth. Intense, throbbing pain can develop immediately upon contact, and other symptoms can include headaches, nausea, vomiting, and sometimes shock or respiratory stress. After my own first (and only) encounter with one of these critters, it took a day for the pain to subside, and several days for the red marks to disappear.

First aid advice for these caterpillar stings includes ice packs, baking soda, and the use of adhesive tape to pull broken spines out of the skin, but prevention — learning to recognize and avoid these caterpillars — beats every cure in the book. 


Comments always are welcome.

79 thoughts on “You Can Look, But You’d Better Not Touch

  1. Good advice, Linda. Just leave them be. It is quite remarkable how many organisms have developed chemical defences of this nature and they are a reminder that a creature we could easily crush with our boot can inflict serious discomfort verging on agony for some, just by making contact. I can think of a few politicians upon whose pillows I would like to place a couple.

    1. Honestly, having experienced an asp sting, I wouldn’t wish it on anyone. It was akin to an electric shock, combined with a kind of pain I’d never felt. I’d rather sit on a nest of fire ants than experience another caterpillar sting; I can say that with confidence, because I’ve made that kind of contact with the fire ants.

  2. Asps were such a common part of growing up in Texas that we used to threaten girls we didn’t like with them, such as, “I’m gonna put an asp in your hair.” In Junior high school, that usually cleared the room of the presence of the opposite sex.

    1. The one that did me in was only an inch long, and the one I found on the car was smaller than that. To paraphrase the old Chiffon margarine commercial, “It’s not nice to mess around with Mother Nature.”

  3. They’re so pretty — I’m glad you shared this, though I’d probably not be inclined to touch a caterpillar. On the other hand, I might be inclined to brush one off the car! Ouch!

    1. If I hadn’t learned to recognize the asp, I probably would have brushed the latest one off the car. At that point, I’d have learned the lesson, for sure. I had the same impulse to touch the pretty white one I usually experience around cacti, but I’ve learned enough lessons in recent years that I managed to restrain myself.

    1. “Bad Hair Day/Stay Away” sounds like half of a Burma Shave ditty. Maybe the second half could be something like, “This Ol’ Critter’s/Not Up For Play!”

      1. “Burma Shave ditty”
        Now that’s another item only (native-born) Americans “of a certain age” will know! As to “native-born”: or someone like me who travels with a “native-born American of a certain age”.

    1. As you like to say, “Holy Cats!” Your browntail moth caterpillar has two additional strikes against it. For one thing, it’s non-native and invasive, but this is what really caught my attention:

      “The caterpillars are covered with tiny hairs, which are shed and can become airborne, potentially causing a skin reaction like poison ivy and trouble breathing if inhaled… The hairs can land anywhere, including on trees, gardens, lawns, and decks. The hairs remain toxic in the environment for one to three years, and can be stirred up by activities like mowing, raking, and sweeping.”

      At least ours keep their toxic hairs to themselves.

      1. Holy cats is right! Those browntials are real stinkers, and what really breaks my heart is that oak trees—my absolute favorites—are their home of choice. Little blighters.

    1. And their sting is reflexive. My arm came in contact with one on a post as I was getting into my car. I must have brushed it, but I didn’t even see it until after the burning sensation got my attention. I had no idea what had happened. The caterpillar never moved; the hairs did all the work. It’s an effective defense, I’ll say that.

  4. The saddleback sting I got earlier this year wasn’t as bad as I was expecting but I can’t imagine an asp! I would love to just see one, though!

    1. I’ve never come across the saddleback, but it made an appearance in several articles I read about our stinging caterpillars. You should have been here last night; I found two more of the asps hanging around. One was on some concrete steps and one had taken up residence on a railing, but both were under the live oak that’s currently losing some leaves.

  5. Yuck! I don’t guess I’ve ever seen one of these, either when I lived in Texas or since. I’ve heard that certain caterpillars aren’t for touching, but I seem to recall letting our “woolly worms” snake up our arms when we were kids. Fortunately, nothing untoward happened. Those side effects sound like half the drugs currently on the market!

    1. Your ‘woolly worms’ (probably what we called woolly bears) aren’t at all nasty. We always examined their brown and black stripes to see how bad the winter would be. Somehow, the width of the various colors was supposed to predict the season. As for the side effects, I might have been skeptical, had I not had a neighbor who landed in the ICU after an encounter with an asp in Galveston. She recovered, but it took some time.

    1. My impression is that everyone who grew up in Texas and got a little too close to one of these remembers the experience. I found two more last night, and marveled again at how much pain such a small critter can cause. Then, when I was done pondering, I moved my car from its spot under the live oak!

    1. Isn’t that pretty? At first, I thought it was a bit of milkweed fluff that had gotten caught on the grasses. Then, I realized it was alive, and decided that I’d better photograph first and identify later. I’m certainly glad I did.

  6. Great shot of that cute and fuzzy creature! I will be looking for asps around our live oak trees as I have encountered them before but didn’t remember their season.

    As I was walking this morning I noticed that some of the live oaks are loosing more leaves than is normal as they lose them in the spring. Maybe they are confused or it is because we have had little rain this fall.

    1. It seems that this is the asps’ season. I found two more under one of our live oaks last night, and when I went out this morning to fill the bird feeders, I found another one. Our live oaks are dropping leaves, too. They usually do have a fall leaf drop; we’ve had plenty of rain, so it must be part of their natural cycle — at least, around here.

    1. Apparently my mother failed to impress the “Don’t touch!” rule on me in childhood. I’m a toucher extraordinaire, even when I know darned well not to ‘do that.’ Faced with cacti, I’m tempted to do the same thing, especially if they’re the sort that have lots of fine spines covering their surface. Some people never learn!

    1. After my own experience with one, a friend advised, “Just think of them as a cluster of hypodermic needles with a load of poison and feet.” That sums it up pretty well.

  7. Your second picture is an effective “Here’s looking at you” portrait. We have to wonder what the caterpillar saw and how it interpreted you. I’m sorry you learned about the asp through painful personal experience. So much in Texas seems to have it in for us.

    1. The caterpillar certainly had an odd little face, but there’s no question it was aware that ‘something’ was hovering over it. As for those painful experiences, that’s how we learn. While I was making coffee this morning I started making a list of Texas realities I’ve learned to respect after a first encounter: fire ants, bumble bees, bull nettle, poison ivy — even dewberry vines. I’m sure there are other “Oh, whoops!” experiences waiting out there.

    1. You might mention to your friend that the asps don’t necessarily hang out only in trees. The one that got me had crawled up a metal post in my covered parking area. I brushed my arm against it as I was getting out of the car. I found one on a sidewalk last night, and one on a metal railing. For such small and apparently slow critters, they certainly do get around.

    1. I didn’t know about them until moving to Texas, and even then, it took a lot of years here — and a too-close encounter of the stinging kind — until I realized they exist. Around here, they seem to prefer the live oak trees in our landscape. I suspect they might start showing up beneath the trees when the oaks begin dropping their leaves. They may well be on those leaves; can you imagine their shock when they’re suddenly flying through the air?

  8. Apparently they are a painful version of “Don’t mess with Texas”. What happens when one touches their hairs reminds me of what happens when one touches the hairs of stinging nettle. Nasty ouch from them both.

    1. Oh, my. On a one-to-ten pain scale, I’d put stinging nettle and bull nettle at about a short-lived seven. The asp? Clearly, an eleven. I’ve never experienced anything like it. It sounds like kidney stones or shingles might be good analogies. I was lucky; the pain subsided fairly quickly, but I sure won’t mess with one of those caterpillars again.

      1. Well then, I am glad to not have them here. I see on BugGuide that they reash northward as far as New Jersey. As we warm up they might spread their range up here but that may be after my time. I won’t be sorry to miss the experience. Reading/watching one article from your Channel 13 news about them it sounds like the pain starts bad enough but grows over time. You were lucky it passed so quickly.

        1. Down at the end of the comments, Yvonne just left her first-person account of landing in the ER after being stung. She went to a clinic first, and they didn’t recognize what had happened, so the trip to the ER was a good move.

    1. Don’t they? They remind me of Fuzzy-Wuzzy the bear, even though these caterpillars have wonderful hair:

      “Fuzzy Wuzzy was a bear,
      Fuzzy Wuzzy had no hair,
      Fuzzy Wuzzy wasn’t fuzzy,
      was he?”

    1. I’ve always known you were a reasonable woman, Ellen. From what I’ve seen over the past few days, there’s no shortage of these little beasties, and I don’t need them on my doorframes or car, thank you very much.

  9. When you look at the face in your second photo, it looks positively evil, Linda. If I saw the face first, there is no way I would touch the caterpillar. Maybe that’s the idea. Fortunately I have never had contact with a stinging caterpillar. Years ago when I learned about them, I adopted a policy that all caterpillars sting. Kind of like Liberians and snakes. All snakes are poisonous. –Curt

    1. That’s a perfect analogy, Curt. I learned early on that the cry of “SNAKE!” would bring a half-dozen machete-wielding friends. Even if I didn’t know them, they were my friends at that point. Whack first, identify later, wasn’t the worst rule in the world, even though a few non-lethal snakes probably met an unfortunate end. I’ll tell you this — these caterpillars put fire ants to shame.

      It did occur to me today that I’ve had an encounter that actually was more painful, and far more dangerous: a bite by a brown recluse spider. It got me near my knee, and within a half hour I hardly could walk. I’ll spare you the whole story, but I sure was glad to find a doctor from Pakistan in a neighborhood clinic who took one look and managed to keep me out of ICU.

      1. Laughing, my ex-wife JoAnn went after a green mamba with a machete with all of the passion that Peggy goes after spiders with a flip swatter.
        Brown recluse… Downright dangerous. Don’t know if I ever seen one. I’ve associated with black widows all my life and they are dangerous enough. So far I have managed not to be bitten by one. But even the normal garden variety of spiders can carry a wallop.
        I did get chomped by a driver ant! None of these can match up to your recluse, however. –Curt

    1. I’m glad to have introduced them to you. Take a look at this article. I doubt you’d run into one in the gardens, unless there are nearby or overhanging trees. I found more today on live oak leaves that had been shed, and a friend found some on her hackberry trees.

    1. ‘Alienesque’ is such a wonderful word. I’ve never come across it before — is it one you invented? It certainly fits these creatures that are capable of sending humans into arabesques of pain!

  10. Good post about the caterpillar moth which is so unusual in appearance. Actually another good find for you. I was stung by the puss moth about 15 years ago, I went to an urgent care and I was given an oral steroid and Motrin to take for pain. After several hours I became very ill- the pain was extremely intense and my head began to throb. I then went to the hospital ER and a very smart MD knew exactly what an asp sting was. The previous MD did not know what I was talking about. At the hospital I was given a steroid injection and IM Demerol. My systolic BP was almost 200 and I was not allowed to go until my blood pressure dropped to an acceptable rate.

    1. I’m glad you were smart enough to get that second opinion quickly, and I’m glad the MD recognized the sting for what it was. By the time you got to the hospital, had the red marks emerged, too? They’re not always just spots; a neighbor who brushed her arm over one had marks that looked like tire tracks for several weeks.

      When I took a look around this morning, I found two more. I don’t know if they’re more common this year, or if I’m just more aware of them. In either case, I intend to avoid them.

      1. My inner left arm had a large red area that hurt with an intensity that I still remember. I had no choice in getting a second opinion. The pain was unbearable and I felt that I was about to faint any minute. My daughter who happened to be home from college drove me both times. Believe me when I say, you just do not want to ever get a sting from one. A bee and wasp sting is much less painful.

        1. I’m glad your daughter was around to help out. When pain sets in, it’s hard to focus on anything else, let alone driving. When it comes to once in a lifetime experiences, a sting from one of these should qualify — although never in a lifetime would be even better.

      1. I have not forgotten that asp sting and never carry an arm full of weeds anymore. I had pulled weeds in my little garden and and I had rolled up my long sleeve shirt above my elbows. The asp stung me on my left inner arm between elbow and wrist. I knew it was an asp as soon as I was stung. I just happened to know about the puss moth I suppose from reading or general knowledge.

        1. The takeaway is to work with sleeves all the way down and wear gloves. I usually do even in July but sometimes we forget. Between you and Linda I am convinced the asp is terrible and something I hope to avoid. They are not this far north but with the warming climate ranges change.

  11. One of my least favorite critters!
    Brushed up against one when I was young and decided I didn’t want to do that again.

    Thank you for a valuable public service announcement!

    Good photographs of a bad bug.

    1. Everyone who’s encountered one of these says the same thing: Never again, thank you very much.
      They are rather appealing little beasties, but all that fuzz and fluff conceals a terrible reality. I have wondered whether the white fluffiness of that black-waved moth is meant to trick predators into thinking the caterpillar’s a dandelion.

    1. No, you certainly wouldn’t! What’s so funny/amusing about them is that they don’t have to expend any energy in attacking. Their little quill-like needles do the work for them.

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