Puss Caterpillar Stings Visitor to San Antonio River Walk 3

This article by Jerry Cates and Michelle Sparks, first published on 17 November 2012, was last revised on 29 November 2012. © Bugsinthenews Vol. 13:11(03).


On 12 November 2012 Michelle Sparks wrote:

“Hi, Jerry:

I’m not sure if you’re still collecting encounter reports on the puss caterpillar, but if you are, I thought I should add my experience to your report.

My husband and I live in Phoenix, but we visited San Antonio this past weekend, and had dinner at a restaurant along the River Walk. It was a nice restaurant with an open patio. I had a sweater with me, as temperatures were brisk. I didn’t notice that the sweater had fallen to the floor while I ate and talked with friends. Afterward, on leaving the restaurant, I put the sweater over my arms and we drove to another place. Soon afterward I noticed that my right forearm, near my elbow, began to burn and become painful. I thought maybe I’d brushed up against a bush or something. As soon as it was convenient, I washed the burning area on my arm well with soap and water and took a Benadryl tablet, but the burning continued to progress. The pain spread up my arm, over my shoulder, into my arm pit, and from there into my chest.

Nothing really showed on my arm, really. Just some tiny “goosebumps” about the size of a tennis ball. Nobody I showed the sting site to recognized it as a sting, but because the pain kept getting stronger I put ice on the sting site, which helped some with the burning. The pain was similar to a broken bone, and I had significant swelling through my hand. I also had so little strength in my hand that I couldn’t hold a fork or knife.

As the pain continued to worsen, I began to wonder if I was suffering a heart attack. Our friends drove me to the nearest Emergency Room where the doctor immediately recognized that I had been stung by a tree asp. I had not seen a caterpillar at the restaurant, and though we closely examined the sweater we did not find a caterpillar on it either. I am planning to throw away the sweater, assuming that it likely has barbs from the now-gone caterpillar still in it. While at the emergency room I was treated with the iv pain medicine diladid, and the steroid solumedral. I was also given an anti-nausea medication, a steroid prescription, a chest X-ray and a complete blood-work.

The next morning, in our hotel, I awoke with a horrible headache and a case of nausea with vomiting and ongoing pain. It took another 12 hours to feel better. Today, more than 48 hrs later, my hand is still swollen, I still have a headache, and my arm is still hot.

We walked along the San Antonio River Walk again yesterday and saw 4 fuzzy caterpillars along our way. I photographed 2, which I’ve included.

Again, I never saw the one that stung me.

The ER physician pointed us to your website and I read it through. I had no idea caterpillars stung!

I used the tape trick last night- 1.5 days after the sting, hoping it would help.

Thank you for all your research on this nasty bug.


Michelle Sparks, Phoenix, Arizona”

Puss Caterpillar sting; 09 Nov 2012; Michelle Sparks; San Antonio, TX River WalkPuss Caterpillar sting; 12 Nov 2012; Michelle Sparks; San Antonio, TX River Walk + 75 hours later



Caterpillar 1; 11 Nov 2012; Michelle Sparks; San Antonio, TX River Walk

100. Caterpillar 1

Caterpillar 2; 11 Nov 2012; Michelle Sparks; San Antonio, TX River Walk

101. Caterpillar 2

Michelle’s experience is essentially identical to that of the hundreds of puss caterpillar sting victims I’ve corresponded with over the past decade and more. The photos she took of two caterpillars found on the San Antonio River Walk two days after she was stung are of urticating caterpillars, and at least one of them (fig. 100) is very likely a puss caterpillar in the genus Megalopyge. I am using her encounter report as an opportunity to update the information previously posted on bugsinthenews regarding this noxious insect. Hopefully, much of the necessary revisions will be completed by Sunday, 18 November.


(1) It is disappointing to note that the emergency room physician who correctly diagnosed Michelle’s sting, and then administered and prescribed medications such as dilaudid and steroids, failed to take steps known to be capable of removing the caterpillar’s toxic spines from the sting site. The most common method for removing the caterpillar’s spines is to gently, but repeatedly, apply and remove a strip of adhesive tape over the sting site. All of the exposed microscopic, toxin-filled spines can be withdrawn from the sting victim’s skin in the process, immediately granting pain relief in the process. Read my comments about poultices, that some have used to deal with the residual pain after taping the site, in the comments section below this article.

(2) Michelle stated she was going to throw the sweater away, but I recommended against that. A good dry cleaning or laundering should be enough to remove whatever spines might remain in the sweater material (most likely none remain at all).

(3) Michelle indicated, in a later e-mail, that she and her husband were visiting San Antonio to see if they might relocate to that city from Phoenix, but now she was having second thoughts. I pointed out to her that puss caterpillars are found all over the United States, including Phoenix, and that most residents of San Antonio have never seen one of these critters. So her second thoughts on relocating to that beautiful Texas city are misplaced. Within hours of posting this article a report was received from Orlando, Florida (home of Disney World) about a puss caterpillar sting that took place there that day. I regularly receive reports of puss caterpillar stings from some of the most popular and beautiful cities in North America. The painful experience those stings produce (not to mention the emergency room and hospitalization expense, which can run into tens of $thousands if the E.R. physician does not recognize the cause of the pain before ordering a battery of unnecessary tests and scans) makes for bad memories that detract from a locale’s allure. Still, such stings can happen almost anywhere in the U.S., Mexico, and Central and South America.

(4) Because puss caterpillar stings are accompanied by excruciating pain, they masquerade as a serious medical crisis (but see note 5, below). This leads the victim to seek professional medical intervention, which often results in staggering medical bills and hours of uncertainty while awaiting the results of hastily ordered tests, scans, and laboratory analyses. Individuals familiar with puss caterpillar stings realize the pain is self-limiting (though it can last for hours, or even days, if nothing is done to remove the microscopic spines from the skin), and that much can be done to reduce or bring the pain to a stop, by the sting victim and others, through taping and the use of inexpensive and easily prepared poultices (see more on these in my article on Puss Caterpillar Stings–Home Remedy First Aid Measures). Thankfully, puss caterpillar encounters are relatively rare, even in locales where the puss caterpillar is endemic. The downside of this is that few individuals know enough to calm the victim’s fears and point them toward the practical remedies at their immediate disposal.

(5) For some, particularly those afflicted with serious medical conditions and susceptible to allergic reactions and chemical intolerances, puss caterpillar stings — as with envenomations from other arthropods — CAN INDEED represent A SERIOUS MEDICAL CRISIS. Never attempt a home remedy for an envenomation event of any kind for such individuals. Instead, seek immediate professional medical help at the nearest emergency room, hospital, or medical center.


Links:   (1) Puss Caterpillar General Information.    (2) The Puss Caterpillar’s Stinging Apparatus. (3) Puss Caterpillar Extermination. (4) The Puss Caterpillar’s Natural Predators. (5). Puss Caterpillar Stings–Medical Interventions. (6) Puss Caterpillar Stings–Home Remedy First Aid Measures.



  • Kingdom Animalia (ahn-uh-MAYHL-yuh)  — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
  • Phylum Arthropoda (ahr-THROPP-uh-duh) first described in 1829 by the French zoologist Pierre André Latreille [November 20, 1762 – February 6, 1833], using the two Greek roots αρθρον (AR-thrawn) = jointed + ποδ (pawd) = foot, in an obvious reference to animals with jointed feet, but in the more narrow context of the invertebrates, which have segmented bodies as well as jointed appendages;
  • Class Insecta (ehn-SEK-tuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Latin word insectum, a calque of the Greek word ἔντομον ( EN-toh-mawn) = “(that which is) cut into sections”; comprised of arthropods with chitinous external (exo-) skeletons, a three part body composed of a distinct head, thorax, and abdomen, the midmost part having three pairs of jointed legs, and the foremost part having a pair of compound eyes and antennae;
  • Subclass Pterygota (tare-ee-GOH-tah) — first described in 1888 by Lang, using the Greek roots πτερυξ (TARE-oos) = wing, to refer to insects with wings, or that had wings but in the process of evolution have since lost them;
  • Infraclass Neoptera (nee-OPP-tur-uh) — first described in 1890 by the Dutch entomologist Frederick Maurits van der Wulp (1818-1899) using the Greek roots νεος (NEE-ose) = youthful, new + πτερυ (TARE-ohn) = wing, to refer to winged insects that are capable of folding their wings over their abdomens, in contrast to more primitive winged insects that are unable to flex their wings in this manner (e.g., the dragonflies, in the infraclass Paleoptera);
  • Superorder Endopterygota (ehn-doh-tare-ee-GOH-tah) — first described by the English physician and entomologist David Sharp (1840-1922) using the Greek root ενδον (ENN-dohn) = within + the established expression pterygota (see above) to refer to insects within the latter subclass that undergo complete metamorphosis, i.e., larval, pupal, and adult stages;
  • Order Lepidoptera (lep-uh-DOPP-tur-uh) — first formally described in 1758 (though he coined the expression in 1735, informally) by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Greek roots λεπιδωτος (lepp-eh-DOH-tose) = scaly + πτερυ (TARE-ohn) = wing, to refer to insects with scales covering their wings, i.e., the moths and butterflies;
  • Family Megalopygidae (megg-uh-low-PIDGE-uh-dee) — from the Greek root μεγας (MEG-as) = great, vast, large + the Greek root πυγη (PIDGE-ee) = rump, tail + the Greek patronymic suffix -ιδες (eye-DEES) commonly used in zoological taxonomy to indicate a family name, in reference to a family of moths typically having an exaggerated tail, honoring the fact that these caterpillars often–but not always–trail a conspicuous tail of hairs; this family is presently represented by 23 recognized genera that are found in North America and in the New World Tropics; in North America as many as 44 species have been described, some of which may be synonyms, but all of which are known, while in the larval (caterpillar) stage, to produce extremely painful stings in humans who come into contact with them;




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3 thoughts on “Puss Caterpillar Stings Visitor to San Antonio River Walk

  1. mikesweetwater Nov 17,2012 9:54 pm

    I was a vendor at an outdoor event in Orlando, FL today and had a very similar experience to Michelle, although my symptoms have not been quite as intense.

    I leaned my forearm directly on top of a little white-ish fuzzy caterpillar that looked much like the Puss caterpillars I’ve seen on this site. Pretty much immediately I felt a deep aching sensation emanating from where the caterpillar was and the pain quickly spread up and down my arm, even out to my armpit and what felt like the left side of my chest as well. The pain was surprisingly intense and I’m still dealing with it even now about 12 hours later. Now the pain is primarily just in the spot of the sting and the area of my arm surrounding that area. The pain now feels like a deep soreness under where I was stung.

    After I was stung I took 3 Ibuprofins which were very ineffective for the pain. A vendor next to me rubbed charcoal on the area to try to extract the toxins, I’m not sure if that was very effective. I took 2 Benadryl a few hours after the sting but didn’t use any tape until just about an hour ago. Hopefully after a good night’s sleep the pain will have gone away :/

    Thanks for this site, it has been very helpful to read of others’ experiences.


    Editor’s comments:

    Persons who have been stung by a puss caterpillar should read my article on Puss Caterpillar Stings–Home Remedy First Aid Measures, a link to which is provided in the above article. In summary, many who have been stung by this caterpillar report that using the tape, even several days later, to remove the microscopic spines, helps immeasurably. A few report that taping the site (gently, but repeatedly, pressing and withdrawing adhesive tape over the sting site) provides little or no relief.

    For the latter, one of the various folk-remedy poultices sometimes works. Raw potato and ginger root, ground into a mash with a food processor after adding a very small quantity of distilled water, then applied to the wound site and gently covered with a thin plastic food wrap (NEVER wrap any wound TIGHTLY with any outer covering) to prevent the poultice from drying out during the 3-6 hour application, has worked for some.

    Others mix pure, powdered medicinal charcoal (obtained at a drug store, labeled for poison control purposes; DO NOT use BBQ charcoal for this purpose) with flax seed meal, adding enough distilled water to produce a jelly-like mass (the flax seed jellies up when water is added) that is then applied in an encapsulated poultice to the wound. Note that applying charcoal poultices directly to a wound can result in permanently tattooing the wound with imbedded charcoal particles. To prevent this possibility, a thin layer of muslin or another kind of close-woven cloth should be placed between the charcoal poultice and the wound. The best way to do this is to encapsulate the poultice in the cloth; (1) cut a piece of cloth about six times the length, and six times the width, of the wound site, and adding enough distilled water to wet the cloth; then (2) place a thin layer — 1/4th to 3/8ths inch thick — of the jellied charcoal/flax seed mixture in the center of the wet cloth, and (3) fold the rest of the cloth over the poultice to make a square with eight layers of cloth above, but one layer below; then (4) apply the square over the wound site, with the single layer of cloth against the wound to allow the poultice to draw the toxins out of the skin through that layer of cloth; and (5) gently wrap (NEVER wrap any wound TIGHTLY with any outer covering) the area in thin plastic food wrap to prevent the poultice from drying out during the 3-6 hour application.

    Anecdotal reports have been sent to me extolling the “amazing” capability of the penetrating oil known as WD-40 to produce immediate relief of the pain associated with puss caterpillar stings. The active ingredient list for WD-40 is a trade secret, so it is not possible to assess the risks to human health attending its use in this manner. Persons using WD-40 for this purpose do so at their own risk.

  2. James Delgado Jan 25,2014 2:34 pm


    I remember being stung by one of these (we called them asps) when I was a growing up in San Antonio. Our yards were full of Texas Live Oak trees and even after growing up and spending many years climbing up into and cutting down oaks, I was only stung the one time. My grandfather immediately knew what got me and he used some duct tape on the site first, applying it multiple times. Then he made a paste out of kaolin clay which my grandmother used for facial masks. It worked surprising fast. Within a couple of hours I was back out playing with my friends, although now with a sharp eye open for more of these creatures.

    Moving forward to November of this last year, I was cutting some tree limbs and came across one of these again and decided to try an experiment. I am now 47 and a bit of an outdoorsman, and after catching one and placing it in a jar I came across your detailed information. My wife had never heard about them and she grew up in San Antonio too, but after reading some of your information she thought I was nuts with what I wanted to do – and she’s an RN by the way. Anyway, I managed to get some kaolinite and created a thick paste. I then bought some ginger root and potato and made a poultice.

    OK, I was now ready. I took a pair of forceps and picked up the little sucker and touched him to my right forearm. Wow, it felt like somebody just slapped me real hard almost immediately. Ok, one down one to go. I then took it and brushed my left forearm with the same results – immediate pain. I gave it about 30 minutes and the pain increased to the point I would normally want to get some relief. I never got any pain radiating much more than about 3-4 inches from the site (I have a relatively high threshold for pain.)

    Anyway, I applied the kaolin clay paste to one arm and the ginger/potato to the other after first applying the tape to the affected areas about a half dozen times. Within about an hour both sites were decreasing in pain, with the ginger/potato seemingly slightly better. After hour 2, both sites were almost pain free, but still slightly tender to the touch. We went to dinner and during dinner my wife asked me how I was doing and I told her I so much better that I decided to go to the bathroom and remove the bandaging and wash both areas with soap and water.

    We finished eating and then went home. On the drive home the pain started to return. Once home, I made another series of pastes and applied them, same as before. The ginger/potato was doing slightly better at that point but I went ahead and applied the paste/poultice and left it on for the rest of the evening, only removing it and washing up before going to bed. The next morning I had no pain but did have the red dots showing where the affected areas were. Other than that, I was good as new.

    So, I would recommend the ginger/potato poultice following the tape procedure as soon as you can get it on. Maybe a change and fresh poultice after a few hours but that is just speculation. I think next year I am going to try and make a combination kaolin/ginger/potato with activated carbon poultice and see how that works. I’ll report back at that time.


    Editor’s comment: Interesting experiment, James. Keep us posted on any further experiments you conduct.

  3. jeff weaver Mar 18,2014 8:40 am

    In reply to article on puss caterpillar stings; I have been stung twice on different occasions in Irving, Tx.-and saw the culprit both times. Once, climbing a large oak tree (without a shirt on) I suddenly had a SERIOUS pain/burning on my chest. I looked and saw this sleek, combed-back, grayish furred thing I’ve never seen before on the bark. That couldn’t be it- too cute! The pain brought me down from the tree, and lasted until the next day. I researched them and was I surprised- such a painfull thing, un-noticed! The second one fell from a low-hanging oak branch that I moved, on to my neck under my shirt collar. In the frenzy that followed, I shook it onto the sidewalk, and saw my second gray puss caterpillar. I knew what I was viewing NOW! Same painfull story followed. They are small,SLOW moving, not obvious. Stinging spines on back in the fur I think.

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