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 them 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 disheveled, "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 adult moth is covered in long fur in colors ranging from dull orange to lemon yellow, with hairy legs and fuzzy black feet.
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