You know the saying, "Nature beat him with an ugly stick"? Well, this is about as ugly as you can get. This is what you get when Nature hates you.
These are the larvae of the buck moth, (Hemileuca maia), one of the poisonous caterpillars found in Virginia. (Yes, I did say poisonous.) You do not want to get close to these. See those tufts on the caterpillars? Each tuft is made up of a cluster of hollow, branched spines that are connected to a poison sac. They break very easily if you brush up against them, and the spine essentially injects the poison into your skin and you will think your skin is on fire. Fun!
The caterpillars will aggregate like this but they tend to drop off very easily when disturbed. Hopefully that won't be down your shirt as you walk under an oak tree. These dropped to the ground right after I took this photo. I hope they regroup this afternoon, and then I plan to beat them ugly with a shovel.