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37 <br />callippe and comstocki occur in the San Francisco Bay area. The most recent five-year review <br />for the species released by USFWS (2009) indicates that the two populations occurring in the <br />project region have not yet been taxonomically verified as the rare subspecies, and as of the 2009 <br />review, the USFWS only recognizes two populations of the rare subspecies: a San Bruno <br />Mountain population and a Cordelia Hills population. <br />Due to the high degree of variation exhibited by individuals within a particular population, as <br />well as geographic variation among populations, the limits of the variation have not been well <br />defined and correlated with the subspecific taxonomic categories. As a result, it is often difficult <br />to identify individual specimens and even populations to the subspecific level without examining <br />a long series of specimens to determine which characteristics are prevalent in a particular <br />population. Even then, some populations tend to exhibit more intermediate <br />characteristics. Since wing colors and maculations may fade with age and scales are lost with <br />age, this further complicates making taxonomic decisions at the subspecific level. <br />Life History and Ecology. The Callippe silverspot (Speyeria callippe callippe) is endemic to the <br />San Francisco Bay area. It occurs on hilly terrain within both grazed and ungrazed grassland <br />habitat where its larval host plant, johnny jump-up (Viola pedunculata) grows. The host plant is <br />typically associated with clay soils. Although the larval host plant is perennial, the above ground <br />growth dies back annually so it can typically only be distinguished during the spring and early <br />summer flowering season. Adult butterflies will visit the margins of oak woodlands and riparian <br />areas in search of nectar, rock outcrops, as well as disturbed areas if favored nectar plants grow <br />there. <br />The four primary habitat requirements of the Callippe silverspot are: <br />a) coastal grasslands supporting its larval food plants; <br />b) hilltops for mate location; <br />c) nectar plants in the grasslands or nearby oak woodlands, riparian areas, rock outcrops, <br />or disturbed areas; and <br />d) shelter from on-shore coastal winds.