When you see a fuzzy caterpillar, you probably think it’s pretty cute. Most caterpillars are harmless, and because we know that they turn into butterflies, most people want to let caterpillars live. They’re also more likely to pick up caterpillars in their homes and move them outside.

But not all caterpillars are as harmless as they appear. Underneath that fuzz and fur are venomous spines that can hurt a kid who finds a caterpillar in a home and wants to play with it. While many people are able to identify poisonous snakes and spiders, caterpillars are harder to detect, and not many people know that certain caterpillars are poisonous and will sting people if provoked.

In Houston, it’s not uncommon to see stinging and poisonous caterpillars in homes. At Natran Green Pest Control, we’ve seen plenty of caterpillars in homes and helped homeowners block them from coming into their homes. Our experts have helped hundreds of Houston homeowners learn more about caterpillars and answered plenty of questions.

If you’re prone to finding caterpillars crawling across your kitchen floor, don’t pick them up without reading our guide to asps and other stinging caterpillars first.

What types of caterpillars sting?

If you’re seeing stinging caterpillars in your home, there’s a good chance it’s the flannel moth caterpillar. These caterpillars get their name from the flannel-like appearance of their fuzz. When they’re in their immature stages, these caterpillars have fine hairs which hide venomous spines. If one were to crawl across your arm, you would feel a painful rash and stinging.

Commonly, these caterpillars are called asps, not to be confused with the poisonous snakes of the same name. But these asps are also poisonous, and they’re found all over Texas. In your yard, you may find them under shady trees or bushes, and they’ve also been known to hang out around schools.

Technically, asps may refer to two types of caterpillars:

• Southern flannel moth caterpillar
• Puss moth caterpillar

You’ll know you have a southern flannel moth caterpillar when you see its long, silky-looking hairs that looks as if it could be a tuft or cotton or fur. When it comes to fur color, most southern flannel moth caterpillars are yellow, reddish brown or gray, and sometimes there’s a mix of all different colors. Adult moths will have wings covered by long hairs that are orange at the base and fade to a cream color towards the bottom. The legs are usually colored in a black fur that is striking and makes them stand out.

Lifecycle of a stinging caterpillar in Texas

At Natran, we believe in integrated pest management, which means using a blend of common sense and scientific knowledge to fight pests in the home. Part of that approach means understanding the biology of stinging caterpillars. When we know their lifecycles and habits, we can take steps to make our environments less hospitable for asps and other home invaders. This will cut down on the amount of pest control needed and the likelihood of a full-blown infestation.

You’ll often see adult puss moths come out in the late spring and early summer. When they come out, they’ll lay several hundred eggs in trees. These caterpillars favor oak, pecan, huckleberry and elms, but they’ll lay eggs in mostly any nearby tree. Over the course of the summer, you might see one or two generations of puss moths grow in nearby trees.

Southern flannel moths are more often found in the fall, but they too can still reproduce quickly.

One way to head off an infestation is to plant trees and shrubs away from your home. Instead of planting shrubs along the side of your home, plant them along a fence. If you do have trees and shrubs near the entrances to your home, make sure you keep them trimmed. When trees and plants are trimmed, pesky insects won’t have much of a space to hide. You’ll likely spot asps before they can make their way into your home.

By winter, both southern flannel moths and puss moths will spin cocoons, which can usually be found at the base of a tree or hanging from a shrub’s branch. At the top, you’ll notice a trap door-like structure. That’s where the adult will eventually emerge. The color of the cocoon will usually depend on the color of the caterpillar. The caterpillar will use its own hairs to weave the cocoon, so the cocoon itself could be reddish brown, yellow or gray.

In the early summer or late spring, the lifecycle will repeat itself, which means you’ll see those caterpillars emerge from their cocoons to stay laying eggs all over again.

What damage can asps do to trees?

For the most part, asps and other stinging caterpillars do very little hard to the trees and shrubs themselves. Their stinging is a defense mechanism, so there’s not much of a risk to the trees.

What you can do, however, is be on the lookout for cocoons in the late fall. As mentioned, you’ll notice them at the base of the tree trunk or on the branches of your shrub. While you could just crush them, it’s probably better to just move them away from your home. Caterpillars eat leaves, and they’re not harmful to the overall environment.

Moving them away from your home will help you fight off a potential infestation. Move the cocoons to the back of your yard where they’ll be too far from your home and probably too far from your children as well.

What to do if you’re stung by an asp?

Southern flannel moths and puss moths do have venomous spines on the bottom parts of their bodies, but for the most part, they’re not horrifically dangerous. While it will hurt if you’re stung by one, it shouldn’t lead a trip to the emergency room unless your very young child is stung. A sting from an asp is more in line with a bee sting to a non-allergic person in terms of danger: It will hurt, but it’s easy to care for. If you or your child does have an allergy, however, see a physician immediately.

If you or your child comes into contact with an asp, you will likely feel the stinging sensation about five minutes after contact. It will feel intense and probably throb for some time. If the sting occurs on the arm, you may also feel pain in your armpit. You’ll see little red bumps or spots appear at the site of the stinging. You may also experience headaches, nausea, vomiting, inflammation or swelling of the lymph nodes, shock or respiratory stress.

While this may sound distressing, it’s important to know that most of these symptoms subside within about an hour of the stinging. The red spots will usually go away within a few days, and overall, you shouldn’t experience any lasting damage from an asp sting.

If you or a child is stung by an asp, here’s what to do:

• Apply an ice pack to the sight of the sting. This will help numb the pain.
• Take antihistamines if the pain is more forceful. Any over-the-counter antihistamines will work.
• Some asps have stout spines, which will become stuck in your skin if you’re stung. Use tape to carefully remove the spines from your skin as this will help stop the irritation.
• If you’re allergic to insect bites or stings or if the pain continues, see a physician immediately.

As with most insect bites and stings, the key is to remain calm and act quickly. It may help to lay down and relax for a little while after you’ve been stung. You can let the headache or nausea pass and then get back to your gardening or whatever else you were doing.

How to avoid asp stings

As mentioned, asps are harmless to the environment, and they don’t need to be eradicated from your yard unless there are too many of them. The best thing you can do for your family is to make sure everyone is aware of what asps look like and how to avoid them.

Having asps in the backyard is just part of life for most people in Houston, so teach your kids what the different types of asps look like. You can use books or internet sites to show your kids what to look out for when they’re playing in the backyard. Kids have a tendency to pick up small, fuzzy bugs they find crawling around, so discourage them from doing so to avoid getting stung.

You and your partner should also be aware of what these bugs look like and how to administer first aid if needed. Go over what to do and monitor your trees and shrubs for any signs of these caterpillars or their cocoons.

You should also keep your first-aid kit packed and ready to go with all the essentials in case someone does accidentally pick up an asp. Be ready with antihistamines and ice packs so you can take care of the problem right away. If your child is allergic to bug bites and stings, talk with your physician about any other items you should keep in your home in the event that someone does get stung.

What to do when asps get out of hand?

Overally, southern flannel moths and puss months probably won’t become too overwhelming in your backyard if you’re diligent about keeping nearby trees and shrubs trimmed. You can also use weather stripping around your doors to block up any cracks where caterpillars can slip into your home, and you can repair any holes or cracked siding where caterpillars may slide in. As mentioned, you can also move any cocoons you see to the edge of your property where they will be less likely to get into your home.

Asps are part of life in Houston, so it’s unlikely that you’ll ever escape them entirely. What you can do though is learn to recognize and stay away from them and be ready with a first-aid kit if someone is stung. You can also keep your trees and shrubs trimmed to deter asps from setting up their cocoons near your home.