Oh, the things one can see, as one walks along a barely used dirt/gravel road!
Keep your eyes open for the little things. Or in this case the big things. This is an Imperial Moth Caterpillar (Eacles imperialis), which can reach a length of 4 inches. As it grows it eats the leaves (or needles) of a variety of trees, including pines.
As with some caterpillars, the Imperial Moth Caterpillar is one that has irritating hairs, that cause an itching stinging rash.
The adult of this species, the Imperial Moth, is an elegant yellow, and brownish purple, with an incredible wingspan of 7 inches.
As an adult the moth’s only purpose is to reproduce, and lives a very short life of just one week, eating nothing during that week.
Keep in mind, if you don’t really know what caterpillar it is that you have encountered, it could be one that will irritate your skin. Leave it be. Don’t pick it up.