Florida is home to several species of caterpillars whose contact can cause immediate, painful reactions in humans. These insects are accurately described as venomous or stinging, as they deliver a defensive toxin through specialized hairs or spines that penetrate the skin. Recognition and avoidance of these unique moth larvae are important for anyone spending time outdoors in Florida.
Identifying Florida’s Stinging Caterpillars
A number of moth larvae found across Florida possess urticating hairs that inject venom upon touch. The most notorious is the Puss Caterpillar (Megalopyge opercularis), considered one of the most toxic caterpillars in North America. This larva is stout-bodied, covered in long, silky hairs that give it a deceptively soft appearance. Beneath this dense covering are stiff, venomous spines that readily break off into the skin. Puss Caterpillars are commonly found feeding on broadleaf trees and shrubs, particularly oaks and citrus, with populations peaking during the spring and fall.
The Saddleback Caterpillar (Acharia stimulea) is easily identified by its distinct coloration. It features a brown front and rear end with a vibrant green midsection containing a prominent brown spot, resembling a saddle. Unlike the Puss Caterpillar, the Saddlebackâs venomous structures are obvious, appearing as fleshy, spiny projections near the front and rear. These stinging hairs are connected to poison glands and are often found on host plants such as maples, hibiscus, and palms. The Io Moth caterpillar (Automeris io) also poses a threat, characterized by its pale green body with yellow and maroon stripes, covered in stinging spines.
Understanding the Reaction
The injury begins when a person brushes against a venomous caterpillar. The stinging structures, known as urticating hairs or spines, are hollow and attached to a gland that produces a toxin. Upon contact, the fragile, barbed tips of these hairs break off and embed themselves into the skin, releasing the venom directly into the tissue.
Immediate symptoms involve sudden, intense, localized throbbing pain and a burning sensation that develops into a rash. The affected area shows signs of inflammation, including redness and swelling, which may radiate beyond the initial point of contact. While the pain often subsides within an hour, the rash and swelling can persist for much longer.
Following contact with a highly toxic species like the Puss Caterpillar, systemic symptoms can arise. These reactions include headache, nausea, vomiting, abdominal pain, and swelling of the lymph nodes.
Immediate Care After Contact
The first step after contact is to remove the embedded venomous hairs to prevent further toxin release. Apply adhesive tape, such as cellophane or medical tape, to the affected area. Gently press the tape down and quickly peel it away, repeating the process until all visible hairs are removed. Do not rub the area, as this pushes the spines deeper into the skin.
Once the hairs are removed, wash the area gently with soap and water. Pain and swelling can be managed by applying a cold compress or an ice pack wrapped in a thin cloth to the sting location. Over-the-counter pain relievers, such as acetaminophen or NSAIDs, can help manage localized discomfort. Topical treatments like calamine lotion or a hydrocortisone cream may also provide relief from itching and inflammation.
Seek emergency medical attention if the person experiences signs of a severe allergic reaction, such as difficulty breathing, widespread hives, or swelling of the face or mouth. Medical consultation is also advised if systemic symptoms like severe nausea or headache develop, or if localized symptoms persist beyond 48 hours. Stings near the eye or mouth should always be evaluated by a healthcare professional immediately.