When I read, "Fell on my arms as I walked by, that's how I found them..how gross!", it gave me shivers.* There are thousands of caterpillars that become moths or butterflies.* I've looked at so many that I fear I will dream about them tonight!* :shock:* Too bad you didn't take any pictures.* :(
Here's a couple of unidentified moth caterpillars I found that closely resemble what you found.* These first two are different views of the same species.
Catalpa worm has a light and dark version.
White flannel moth
Dogwood sawfly also comes to mind.* The larvae (caterpillars) change color as they age.
This gallery is of unidentified moth caterpillars if you'd like to look.
Named moth caterpillars
Two pages of smooth caterpillars to look at here.
If none of those fit I can get you more sites to look through.* It probably doesn't matter much as you've already used Sevin which should kill just about any insect, good or bad.* :(
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.