California Sister (Adelpha californica) is a medium-large butterfly, with a wingspan of 2.5 to 4 inches. Adults live for about 30 days, and can be seen in our local area from late March to October. Numbers peak in May-June. Host plants are various oaks, especially Canyon Live Oak (Quercus chrysolepis). The tannins in oak leaves make the caterpillars and the adult butterflies unappetizing to predatory birds.  It usually does not nectar, except in the fall, feeding primarily on rotting fruit, and by mud-puddling (i.e., ingesting nutrients from wet soil). It is exclusively a west-coast butterfly. Adults live for about 30 days.

California Sister can be easily confused with Lorquin's Admiral, especially in flight, since the upper wings look similar. The best way to distinguish them is to look at the orange patch at the tip of the forewing. California Sister has a large patch with well-defined edges; Lorquin's Admiral has a smaller patch that fades away at the edges.

It is found along the west coast of the U.S., from Oregon into Baja California.