Common Name: Serpentine Colorado
Skipper
Populations of Hesperia colorado (as determined by
the genitalia) occur at scattered locations on the Sierran west slope on serpentine substrates and fly in
autumn - mid-September into October. One of these occurs on serpentine along
Washington Road, where it is sandwiched between "normal" populations
of what is now called H. colorado harpalus but used to be called H.comma
yosemite, which fly in June-July both higher and lower but on metasedimentary substrates! The
seasonal displacement of these populations means they cannot exchange genes
with others and they are thus behaving as if they were a species in their own right. Both
sexes are, on average, darker on the ventral hindwing than nearby
early-summer ones. The only nectar source available to these insects is a dwarf
serpentine-endemic ecotype of Rabbitbrush (Chrysothamnus
nauseosus). There are late-flying, very dark populations on serpentine in
far northern California (named as subspecies mattoonorum),
but it is not clear that they are related in any way to these. Molecularly, the
serpentine-autumn populations resemble the nearby summer ones, not the
autumn-flying entity found in the High North Coast Range.