This caterpillar looks and acts similar to black and rust Wooly Caterpillars. It is crawling on pasture grass in northwest Washington State near Snohomish. The date is September 2, 2017.
It does have the similar bands, tho very bleached, to the banded woolly bear caterpillar. The banded woolly bear caterpillar actually has a strange beige coloration that sometimes occurs under very wet conditions. When this happens, it is darker on the head end and the color lightens towards the tail.
All of that said, it is one of the tiger moth caterpillars – over 250 species in North America. We can not see the face color, which would be very helpful for a positive ID.
However, looking at the long hairs of this caterpillar, my best guess is the Virginian tiger moth caterpillar. The tiger moth caterpillars vary a lot in coloration…they can be one color before molting, and then another color after molting. Another common name for this caterpillar is the yellow woolybear.
The adult moth is fluffy white with a few black dots possible on both wings. The abdomen has rows of black spots along the top and sides. On the sides of the abdomen near the black spots are yellow-orange spots. The tiger moths are gentle and will crawl up on your finger if you find one at your porch light.
The Virginian tiger moths are found throughout North America. They are certainly found in pastures as they feed on many low-growing plants like grasses and clover, but also feed on some shrubs, as well as trees.
This insect is not a pest. Just cool to watch.
This caterpillar will not cause a rash or sting.