A Checkered White
I've never seen a Checkered White butterfly Pontia protodice before.
It was visiting our native patch a few days ago.
At first I thought it was a Cabbage White Pieris rapae, because at a quick glance, they look similar, and Cabbage Whites visit the garden throughout the day.
This is a female adult Checkered White.
Males are white with dark grayish brownish spots on their front wings.
These butterflies used to be abundant but now rarely seen.
Here in Northern California, this species is usually found in gently rolling or flat terrain.
It feeds on flowers, fruit and buds, especially on asters, goldenrodsan thistles.
Members of the mustard family such as wild radish and peppergrass act as host plants.