Southern Flannel Moths (Megalopyge opercularis) are often admired for their distinctive, fluffy appearance, yet they frequently prompt questions regarding their safety. These insects, particularly their immature stage, have a reputation that belies their soft exterior, leading many to wonder about potential dangers. Understanding them is important for safe interactions.
Identifying Southern Flannel Moths and Larvae
The adult Southern Flannel Moth is a small, chunky-bodied insect, typically measuring about 1 to 1.5 inches in wingspan, with a fluffy, fur-like covering. Their coloration varies, often appearing golden yellow, whitish, or brownish. While the adult moth is harmless, its larval stage, commonly known as the puss caterpillar, poses a concern.
The puss caterpillar is teardrop-shaped and densely covered with fine, silky hairs, giving it the appearance of a tuft of cotton or fur. These caterpillars vary in color from downy grayish-white to golden brown or dark charcoal gray, sometimes with a distinct orange streak. Hidden beneath these hairs are rows of hollow, venomous spines, which are the source of the caterpillar’s defense mechanism.
Understanding the Sting: Venom vs. Poison
The Southern Flannel Moth larva is not poisonous, meaning it is not harmful if ingested. Instead, it is venomous, delivering toxins through injection. When a puss caterpillar is brushed or pressed against skin, its venomous hairs become embedded. These spines are connected to venom glands containing an urticating fluid. The hollow spines break off in the skin, releasing the venom.
The sting can cause immediate, intense burning and throbbing pain that often radiates to other parts of the body. A swelling, itching rash typically develops, sometimes forming a grid-like pattern of red blotches matching the caterpillar’s spines. Beyond localized pain, some individuals may experience systemic symptoms such as nausea, headache, fever, muscle cramps, swollen glands, chest pain, or difficulty breathing. Recent research indicates that the main pain-causing toxins in puss caterpillar venom may resemble bacterial toxins, specifically megalysins, which can create holes in cells.
Immediate Steps After a Sting
Should contact occur with a puss caterpillar, gently apply adhesive tape to the affected area and pull it off to remove embedded venomous spines. After removing the spines, wash the stung area thoroughly with soap and water. Non-contact drying, such as using a hair dryer on a low setting, can be beneficial.
To alleviate pain and swelling, apply an ice pack to the site for 5-10 minutes every two hours. Applying isopropyl alcohol, a baking soda slurry, or calamine lotion can provide soothing relief. Over-the-counter pain relievers may help manage discomfort. While most stings result in localized symptoms that subside within hours to a few days, seek medical attention if severe reactions occur, such as difficulty breathing, widespread rash, or severe swelling.
Habitat and Prevention
Southern Flannel Moths and their larvae are primarily found throughout the Southern United States, with their range extending from New Jersey to Florida and westward to Arkansas and Texas. They are also present in Mexico and parts of Central America. These insects commonly inhabit wooded areas, deciduous forests, parks, and gardens, often found on various trees and shrubs.
Puss caterpillars feed on a wide array of host plants, including oak, elm, maple, hackberry, sycamore, pecan, rose, ivy, and citrus trees. They are most active from late summer to early fall, when encounters are more likely. To prevent stings, avoid touching any unfamiliar caterpillars, especially those with a furry appearance. When performing yard work or gardening in areas where these caterpillars are common, wearing protective clothing, such as long sleeves, pants, and gloves, reduces the risk of accidental contact.