The caterpillar of the puss moth, Megalopyge opercularis, also commonly known as the asp caterpillar, is one of the most toxic caterpillars in North America. It is endemic to the southwestern United States and Central America, where it is common, and often found on shade trees such as oaks, elms, maple and citrus, or on small bushes. The 2.5-4 cm long caterpillar is covered with silky yellow, grey, red, or mixed color hairs (setae). Although the caterpillar’s appearance is soft and almost like a small furry cat (possibly inspiring its common name, puss caterpillar) its thick setae hide ridges of short, hollow spines connected to poison glands. When touched, these spines penetrate the skin, injecting poison which causes intense pain, nausea, vomiting, headache and sometimes respiratory distress and stings may require medical attention. Recent molts may also cause a sting. Instead of the usual five prolegs of most caterpillars, those within the flannel moth family (Megalopygidae) have seven. The adult moth, called the Southern flannel moth, is also unusually fuzzy in appearance, with and orange thorax and orange at the base of its blunt yellow wings, a 2.5-4 cm wingspan, and little black furry feet.
(Lyon; Eagleman 2008; Hall 2013; Hyche 1998; Wikipedia 2011)
Regularity: Regularly occurring
Type of Residency: Year-round
Confusion surrounding the "Donald Trump" caterpillar
Megalopyge opercularis occurs only in North and Central America, however in 2013 a megalopygid caterpillar filmed in Amazonian Peru by wildlife photographer Jeff Cremer and conservation biologist Phil Torres was erroneously identified as M. opercularis. Because the Peruvian caterpillar bore resemblance to Donald Trump's hairpiece, news media picked up the story and confusion ciruclates that the common name of M. opercularis is the "Donald Trump" caterpillar. Like M. opercularis, the unidentified caterpillar is in family Megalopygidae, and bears venomous spines that can inflict pain on humans or other animals that brush them, but it is a different species, and perhaps different genus of megalopgid caterpillar.
Molecular Biology and Genetics
Barcode data: Megalopyge opercularis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Megalopyge opercularis
Public Records: 2
Specimens with Barcodes: 45
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
The moth Megalopyge opercularis has numerous common names, including southern flannel moth for its adult form, and puss moth, puss caterpillar, tree asp, and the asp caterpillar for its larval form.
M. opercularis is visually striking in both larval and adult forms.
The inch-long larva is generously coated in long, luxuriant hair-like setae, making it resemble a tiny Persian cat, the characteristic that presumably gave it the name "puss." It is variable in color, from downy grayish-white to golden-brown to dark charcoal gray. It often has a streak of bright orange running longitudinally. The 'fur' on early-stage larvae is sometimes extremely curly, giving the larva a cottony, puffed-up look. The body tapers to a tail that extends well beyond the body, unlike its relative M. crispata. The middle instar has a more dishevelled, 'bad-hair-day' appearance, without a distinctive tail.
The 'fur' of the larva contains venomous spines that cause extremely painful reactions in human skin upon contact. The reactions are sometimes localized to the affected area but are often very severe, radiating up a limb and causing burning, swelling, nausea, headache, abdominal distress, rashes, blisters, and sometimes chest pain, numbness, or difficulty breathing. Additionally, it is not unusual to find sweating from the welts or hives at the site of the sting. Ironically, the resemblance of the larvae to soft, colorful cotton balls encourages people to pick them up and pet them.
The adult moth is covered in long fur in colors ranging from dull orange to lemon yellow, with hairy legs and fuzzy black feet.
M. opercularis can be found on oaks, elms, citrus and other trees, and many garden plants such as roses and ivy. It is distributed throughout the southern United States, Mexico, and parts of Central America. The larva does not spin a real cocoon; rather, it separates from its furry skin and uses it as a protective covering while it pupates.
Dangers and treatment of stings
Exposure to the caterpillar's fur-like spines will lead to an immediate skin irritation. The caterpillar is regarded as a dangerous insect because of its venomous spines. Medical advice may be sought in case of contact with one. It is best if the venom from the spines is treated within hours of first contact. For first aid, it is recommended that the spines (if present) be removed by using cellophane tape.
Other remedies, which are reported to have varying degrees of success, include ice packs, oral antihistamine, baking soda, hydrocortisone cream, juice from the stems of comfrey plants, or calamine lotion.
- Wagner, DL (2005), Caterpillars of Eastern North America., Princeton Univ. Press
- Eagleman, DM (2007). "A Study of the Geographical Distribution and Symptoms of Envenomation by the Asp Caterpillar, Megalopyge opercularis". Clinical Toxicology 46 (3): 201–5. doi:10.1080/15563650701227729.
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