Euchloe lotta nr belioides
For now, the desert species of the lotta/hyantis group best fits here. See the discussion under nom. hyantis for more detail. The literature on this complex of butterflies involves a mix of incomplete DNA work, some often questionable reliance on phenotype, and some very good field observations that suggest we are dealing with at least a couple of species. As an example, E. hyantis andrewsi flies in June along the highway near Lake Arrowhead in the San Bernardino Mountains. It is known to be distinctive and possibly imperiled. Not far from there, another "Pearly Marble" is quite common on the east side of Big Bear Lake. I have it as E. hyantis hyantis per Ken's tentative arrangement, but it isn't tenable to put both entities in the same species when they clearly are distinct and basically sympatric. It also appears that these desert lotta differ from hyantis, and both Ken and Jim Brock "have both noted that hyantis and lotta both occur together along the Chimney Peak Road and in the Kennedy Meadows area on the Kern Plateau" (Emmel update, p.58). The limited DNA testing on Euchloe* provided some clarity, with the authors "asserting that biological and phenotypic characters indicate that species-level isolation has been attained for E. hyantis, E. lotta Beutenmüller, 1898 and E. andrewsi Martin, 1936, respectively" despite "no or little sequence divergences for members of the Euchloe hyantis complex." That, however, is limited to mtDNA/COI analysis. Bottom line for those of us in southern California: at least three species in a complex of related butterflies works with what seems to be going on in the field.
*Werner Back, Michael A. Miller, and Paul A. Opler "Genetic, Phenetic, and Distributional Relationships of Nearctic Euchloe (Pieridae, Pierinae, Anthocharidini)," The Journal of the Lepidopterists' Society 65(1), 1-14, (1 March 2011).