The next photo will give away part of the answer:
A small caterpillar was feeding on the outer layers of the Coast Buckwheat leaf. I'm guessing the caterpillar is either a blue or a hairstreak. Unfortunately, I'm not sure which one. If you know which butterfly this is, let me know, and I'll post the answer!
Photos from the Pinnacle Gulch Trail on 19 June 2015.
P.S. Click on the names for an example of an Acmon Blue, a Gray Hairstreak, or a Coast Bramble Hairstreak.