I set up the lights and sheet tonight and a couple of these showed up. They remind me of sleepy buffaloes - so docile in the morning.
"Lappet" either refers to the hind wing that hangs down below the costa (leading edge of forewing), OR, perhaps, the flaps on the sides of the larvae.
I was with some friends in Rhode Island for the 4th of July (2004) and this Lappet caterpillar was discovered making its way across the deck.
When we went to move it, it reared up in this defensive pose - pretty impressive!
