Megalopyge opercularis is a moth of the family Megalopygidae. It has numerous common names, including southern flannel moth for its adult form, and puss caterpillar, asp, Italian asp, Fire caterpillar, woolly slug, opossum bug, puss moth, tree asp, or asp caterpillar.
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.