Every night it sounded like there was a slow, gentle rain falling on our tent. But there was no rain, there were barely any clouds in the sky. I think the sound was that of frass (caterpillar droppings) falling from many unseen caterpillars in the Hackberry tree by our tent.
White-marked Tussock Moth - Orgyia leucostigma
Tussock Moth family, Lymantriidae. Feeds on a wide variety of woody plants.
Pale Beauty - Campaea perlata
Looper, Inchworm and Spanner family, Geometridae.
Grapevine Skeletonizer - Harrisina americana
Leaf Skeletonizer family, Zygaenidae. Feeds on Grape vines and Virginia Creeper.
Banded Tussock Moth - Halysidota tessellaris
Tiger, Lichen and Wasp moth family, Arctiidae. Feeds on a variety of woody plants. The individual pictured above is missing most of its hairs, which are technically called setae. We found one other Banded Tussock Moth caterpillar that was in a similar state. The missing hairs might be caused by birds trying to eat them.
"Caterpillars of Eastern North America" by David L. Wagner