Puss Caterpillars (Asps): Texas's Furry Stinging Caterpillar
The soft, teardrop-shaped tuft of tan, gray or rusty "fur" crawling on an oak, elm or shrub is a puss caterpillar, which Texans call an asp. Under that hair are venomous spines that cause sudden, intense pain when touched. The answer for most families is learning to recognize them and keeping hands off; if one stings, get the spines out with tape, ice the spot and watch for allergic signs.
Concerned about stinging pests around your home? Call or text (210) 281-1064 or book a visit.
What does an asp look like? #
The Insects in the City fact sheet on stinging caterpillars describes asps as teardrop-shaped, with long silky hair that makes them look like a tuft of cotton or fur.
- Size: a mature caterpillar is 1 to 1 1/2 inches long.
- Color: yellow or gray to reddish brown. AgriLife's venomous animals bulletin says most are tan or gray, with the hair lying flat.
- The catch: the venom spines are hidden under that soft-looking coat.
The adult is a moth, the southern flannel moth (Megalopyge opercularis).
A Texas A&M entomology article sums it up: these caterpillars look touchable, but they aren't. That's the message every child in a Texas yard needs to hear.
Which trees and shrubs do they live on? #
AgriLife lists a range of common host plants around Texas homes:
- oaks
- pecan
- elm
- hackberry
- dwarf yaupon and other shrubs
- palms and holly, per AgriLife's venomous animals bulletin
That list matters because the worst encounters happen close to home. A <a href="https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=29625901&rettype=abstract&retmode=text">Texas DSHS study of poison center calls found 91 percent of reported stings happened at the person's own residence.
Caterpillars sometimes drop from branches, so the space under a shade tree, a play set beneath an oak, or a patio chair next to a hedge are all places to look before kids settle in.
When are asps worst in Texas? #
AgriLife describes the yearly cycle this way: adult moths come out in late spring or early summer and lay several hundred eggs on favored host trees. There are one or two generations each year, but the caterpillars tend to be more common in fall. They spend winter as pupae inside cocoons stuck to the trunk or branches of the host plant.
The DSHS study backs that up with real numbers. Of 3,484 stings reported to Texas poison centers from 2000 through 2016, 12 percent came in July and 59 percent in October and November.
| Time of year | What to expect |
|---|---|
| Late spring to early summer | Moths emerge and lay eggs on host trees |
| July | A smaller summer bump in reported stings (12%) |
| October to November | The heaviest season for stings (59% of reports) |
| Winter | Pupae in cocoons on trunks and branches |
In practice, that means fall is the time to look over host trees, the ground beneath them and anything kids touch outdoors before they head out to play. A quick check in midsummer is worthwhile too, since July shows its own smaller rise in reports.
What does a sting feel like? #
When skin brushes an asp, the spines snap off and release venom. The DSHS study lists severe pain, redness, rash and other effects. Insects in the City says intense, throbbing pain starts right away or within about five minutes. In most cases the pain fades within an hour and the marks clear in a day or so, though AgriLife's bulletin notes a rash can sometimes linger for hours or days.
Less often, people get a headache, nausea or vomiting, and occasionally shock or difficulty breathing.
Even a dead caterpillar or a cocoon can still cause a reaction, according to AgriLife's bulletin.
The good news in the DSHS data: 89 percent of reported stings were managed outside a hospital or clinic, and 93 percent caused no effects or only minor ones.
If you're curious why the sting is so strong, a 2023 study in PNAS traced the venom's pore-forming toxins, which researchers named megalysins, to genes the moth's ancestors picked up from bacteria.
First aid for an asp sting #
AgriLife's advice, step by step:
- Shake the caterpillar off right away if you can, without using your bare hand.
- Press tape against the skin and peel it off to pull out any spines left behind.
- Put an ice pack on the area.
- An oral antihistamine can help with itching and burning; follow the package directions.
See a doctor immediately for signs of an allergic reaction, such as itching that spreads over the body or trouble breathing. Any sting to the eye should go straight to an eye specialist. The Texas Poison Center is 1-800-222-1222.
Everyday prevention #
- Wear gloves, long sleeves and long pants for yard work near host trees and shrubs.
- Don't sit or let kids play directly under trees where caterpillars may fall.
- Teach children to recognize asps and leave fuzzy caterpillars alone.
- Don't touch dead caterpillars or cocoons, even with a fingertip.
- Check outdoor furniture, play equipment and toys that sit under or near host plants.
Insects in the City suggests that on playgrounds, teaching people not to touch the caterpillars may be the most practical solution of all.
Should the trees be sprayed? #
Insects in the City says asps seldom do serious damage to trees, so spraying out of fear isn't needed. AgriLife does note they can be controlled with a residual spray when they become abundant. That kind of tree and shrub work, though, falls under the Texas Department of Agriculture's lawn and ornamental license category, which Pest Trappers does not hold. We don't spray trees or shrubs, and we'll tell you so up front. If you decide a heavy infestation on a tree near a play area needs spraying, ask a company that holds the lawn and ornamental category for that part of the job.
How Pest Trappers handles puss caterpillar concerns #
What we can do is inspect your home and the structures around it: the house exterior, porches, patio covers, play equipment, sheds and fences. The technician confirms what you're seeing, explains the options for treating around the structure and for any other stinging pests found, and applies any product strictly according to its label. For the trees themselves, we'll share the prevention steps above.
Pest Trappers LLC (TPCL #0887549) is licensed for general pest and termite work. We give pricing after the inspection; call or text for a quote.
Local pages: San Antonio, Boerne, Leon Springs and The Dominion and Fair Oaks Ranch.