This small cricket was nibbling away at the margin of the petal. Later he moved to the center of the flower and began to eat the pollen.
The flower is Calandrinia ciliata, or Red Maids. I was not familiar with this flower until Friday, when I saw a photo posted by ParsecTraveller. The next day, on Saturday, I was hking in the Arastradero Preserve in Palo Alto when I saw the flower for myself.