(I know “Butterfly Mariposa” is redundant, so is “The La Brea Tar Pits”, I didn’t name it).
This species is quite variable. West of Forbush I’ve only seen white flowers without a secondary spot on the upper petals. At Forbush I’ve seen a mixture of plants with and without a secondary spot. Along Blue Canyon trail the petals got less white, and by Cottam camp they were mostly pink.
It blooms in late May and early June. Found scattered around Forebush camp ground, and on Matias and Arroyo Burro (back side) trails. No signs of blooms on 22 June.
It seems to start each morning in a tight curl, then unfurl as the day gets warmer, and then curl up again around 4 or so.
Early in the year it is said to produce a basal leaf, but by the time the blooms happen there is only a spindly stalk topped by a large flower.