Texas has more than 50 species of stinging caterpillars, and experts say people are most likely to encounter them from April through June.
One of the more common species found in the Houston area is the asp caterpillar, or puss caterpillar. Wizzie Brown, a senior extension program specialist with Texas A&M AgriLife Extension Service, said it's also known as the Southern flannel moth and has a deceiving, fur-like covering that can appear inviting.
"They are a teardrop shape. They look very, very soft, like you should touch them, but you should not," Brown said. "Those are found a bit west of I-35 and then east in Texas. They cover a really large area."
Other stinging species found in Texas include buck moth caterpillars, io moth caterpillars, hag moths and saddleback caterpillars. Brown said the species are not considered invasive and usually keep to themselves, living in large trees.
"A lot of them are going to be in broadleaf trees, and most of the time, if it's a mature tree, you don't really know that they're there," she said. "Usually when people call us about stinging caterpillars, it's either that there are extremely large numbers of them, or somebody set up a seating area underneath a tree and the caterpillar fell on them while they were sitting there."
The majority of these caterpillars use a similar method of delivering their venom, Brown said.
"So generally with the stinging caterpillars, they have some sort of spine on their body that is attached to a venom gland," she said. "When you touch that spine, the spine can either inject the venom or it will break off, and the venom will spread on your skin, and that can cause a reaction."
The severity of the sting depends on several factors, and Brown said the reaction can differ from person to person.
"Depending on who you are and how your body reacts to that particular venom, it could be anything from maybe localized pain, swelling, redness, to a rash, to even more severe reactions if you have an allergic reaction to it," she said. "This goes for anything that can inject venom, whether that's by stinging or biting.
"You want to monitor your health, or your kids' health, and if you have abnormal swelling or excruciating pain -- or if you have heart palpitations or breathing problems or anything like that -- you would need to seek medical attention," Brown added.
For homeowners, it can sometimes be difficult to deal with an infestation if the caterpillars are in a large, mature tree, but Brown said a specific type of bacterium, called Bacillus thuringiensis kurstaki, can be used to kill the caterpillars.
"They do have to ingest enough of the product from them feeding on the foliage, but it's only going to kill caterpillars," she said. "So, it's a way you can control caterpillars without harming beneficial insects that might be helping you manage those populations."
Overall, Brown said the caterpillars typically do not bother people, and they all stop being venomous once they become moths.