It’s prime caterpillar season these days! I’ve had several identified through the good folks at the Insect Identification FaceBook page. So far, the nicest one is the Viceroy caterpillar.

Commonly called the Bird-poop caterpillar for its camouflage, this little guy becomes the lovely Monarch mimic, the viceroy butterfly.
I looked more carefully at the plants after finding the viceroy, and saw this willow sapling with a lot of damage. But look closely…

These funny little guys are Furcula species. They freeze when the sense danger, then throw that little tail up as a threat posture when I get closer. The black ones are newly hatched. These become a cute grey and white moth.

I spotted Virginian Tiger Moth caterpillars (Spilosoma virginica) chowing down on the dogbane (Apocynum cannabinum), but the only thing eating the milkweed is a ton of orange oleander aphids and a few milkweed bugs (Lygaeus species).
If you want to have a “cat” hunt in your yard, look for damaged or missing leaves and then look closely under the remaining leaves, along the stem, and anything that isn’t plainly a clean leaf. You might be surprised at what you find!
Update 18-Aug-2017
The furcula caterpillars are highly sensitive to noise, especially cattle-dog barks! I took this video Friday evening.
There is a new instar in the video, maybe this is the last before they pupate.