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The southerly flannel moth caterpillar hides a collection of awful spines under it soft hairs. Image: M. Merchant

Most stinging caterpillars belong come the insect family known together flannel moths. Flannel moths get their name from the flannel-like appearance of the wing of the adult, which space clothed with loose scales blended with long hairs. The immature stages of flannel moths space caterpillars which are clothed through fine hairs and also venomous spines. The spines, once brushed versus the skin, create a painful rashes or sting. The finest known flannel moth and stinging caterpillar in Texas is the southerly flannel moth, or puss moth caterpillar, Megalopyge opercularis. In Texas this caterpillars are frequently known as “asps”. This caterpillar is often abundant and may infest the shade trees and also shrubbery approximately homes, schools, and in parks. They are of minor prestige as enemies of the shade trees, yet they can cause a severe sting. When a puss moth caterpillar rubs or is pressed against skin, venomous hairs stick into the skin resulting in a major burning sensation and also rash.

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Southern flannel moth caterpillars room teardrop-shaped, and, with their long, silky hairs, resemble a tuft of cotton or fur. Their color varies native yellow or gray to reddish-brown, or a mixture that colors. The maturation larva is 1 to 1 1/2 inches long with seven pairs the prolegs (suction-cup favor claspers, on the rear half of the body). The adult moth has blunt wings covered with long, wavy hair and also a wingspan that 1 come 1 1/2 inches. Wings room orange at the base, fading come cream-colored at the tips, and also the legs space covered v delicate, strikingly colored hairs. Other usual stinging caterpillars in Texas include the Io moth, buck moth and saddleback moth caterpillars.



Adult moth that the southern flannel moth, Megalopyge opercularis, photograph by Laura Bellmore.

Adult puss moths emerge in late feather or early summer to lay number of hundred egg on favored host trees, such together oaks, pecan, elm, hackberry and also other trees. Caterpillars may likewise be viewed feeding ~ above dwarf yaupon and other shrubs. One to two generations happen each year, though southerly flannel moth caterpillars often tend to be an ext common in the fall.

The caterpillar safety the winter in ~ a unique-shaped cocoon. Cocoons deserve to be found on the stems or branches that the host plant. At one finish of the cocoon a trap door is listed for the escape of the adult as it emerges from the pupal case. The dorsal surface of the cocoon is marked by a structure comparable to a sheet scar. The shade is around the exact same as the of the larva, due to the fact that the larval hairs are included in the silk.


Puss moth caterpillars rarely reason serious damages to trees; yet they can pose a health and wellness hazard come children and gardeners. Intense, throbbing pains develops instantly or within five minutes of contact with the caterpillar. Stings top top the arm may also result in pains in the axillary (armpit) region. Erythematous (blood-colored) point out may appear at the site of the sting. Other symptoms include headaches, nausea, vomiting, lymphadenopathy, lymphadenitis, and also sometimes shock or respiratory stress. Pain commonly subsides in ~ an hour and spots disappear in a work or so.

First Aid


Stings native the southerly flannel moth caterpillar

An ice fill should be applied to the site of the sting, and also oral antihistamines have the right to be administered to aid relieve the itching and also burning sensations. Because that caterpillars with stout spines (such Io moth and saddleback caterpillar), try carefully using cellophane ice to, and also stripping that from, the sting site. This helps eliminate the irritating spines. For allergic reactions, together as generalized itching or challenge breathing, watch a physician immediately. For serious pain medical professionals sometimes provide meperidine HCl, morphine, or codeine; aspirin is apparently not effective. Eye injuries should also be described a specialist immediately.


Puss moth caterpillars can be controlled when they become abundant by spraying with a residual pesticide such together permethrin, cyfluthrin or comparable sprays labeled for regulate of caterpillars on ornamental plants. In some cases, such as on institution playgrounds, the finest solution might be educating students and also teachers on what the caterpillars are, and also the prestige of not emotional with bare hands.

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For an ext information

First aid information in this publication is based upon recommendations released in the Physician’s guide to Arthropods of medical Importance (Jerome Goddard, 1996, CRC Press, second Ed.). For much more information ~ above stinging caterpillars inquiry publication L-1312, Stinging Caterpillars, indigenous your regional county expansion office. This publications, and help with added questions about asps or other pest problems, deserve to be derived by contacting your county expansion office.


Michael Merchant, Ph.D., Professor and also Extension city Entomologist, Texas AgriLife expansion Service