Lappets are hairy lobes, and the caterpillar for this moth has them along the sides of its body. The gray body may have a green or blue hue to it. Some have orange fringe near the legs, others have orange flecks of color on their 'back'. The level of black and white markings varies among individuals; some seem black with white marks, while others seem the reverse.
When threatened, it stretches it body to expose two red or orange bands by the head. This is a useful feature for identifying it. It typically rests during the day by aligning itself on a branch or twig, the hairy lobes blurring the line between it and the branch. This camouflage allows it to rest in relative safety until night when it actively feeds on leaves of its host plant. Photos of people handing the American Lappet caterpillar without gloves exist and no adverse effects were noted with them for this particular species.
The map above showcases (in blue) the states and territories of North America where the American Lappet Moth Caterpillar may be found (but is not limited to). This sort of data can be useful in seeing concentrations of a particular species over the continent as well as revealing possible migratory patterns over a species' given lifespan. Some species are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America.*NOTE: States/Territories shown above are a general indicator of areas inhabited by the American Lappet Moth Caterpillar. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.