You can't miss this big caterpillar - it's lime-green! And it has little yellow and black antennas, and white spiky bumps, and lots of green feet.
At first I thought it was the caterpillar of a Hummingbird Moth but the markings were a little off. Then I thought of the huge Ceanothus Moth and...bingo!...I had the answer. This is the caterpillar of that beautiful moth.
Here is what this caterpillar becomes, photographed by Clay Yale. What a transformation!
Thanks to Peter and Clay for allowing me to share their photos with you here.