'Desert' Black Swallowtail - Papilio polyxenes coloro
A fresh Papilio polyxenes coloro perching along Cactus Spring Trail, April 27, 2017.
'Desert' Black Swallowtail - Papilio polyxenes coloro
Here's a coloro nectaring on the same trail a week earlier, April 22, 2017.
'Desert' Black Swallowtail - Papilio polyxenes coloro
A hungry last-instar coloro larva was munching host Thamnosma montana right at the trailhead on the same hike as above.
'Desert' Black Swallowtail - Papilio polyxenes coloro
A closer look at the same caterpillar.
'Desert' Black Swallowtail - Papilio polyxenes coloro
A very cooperative Papilio polyxenes coloro at gravel along Horsethief Creek, which is down Cactus Spring Trail in Riverside Co. September 20, 2014. This one didn't move for five minutes; not my usual experience with these. These can be very small, and this one looked not much larger than a Painted Lady.
'Desert' Black Swallowtail - Papilio polyxenes coloro
This 'Desert' Black Swallowtail - Papilio polyxenes coloro - was hilltopping above Palm Springs. September 4, 2010.
'Desert' Black Swallowtail - Papilio polyxenes coloro
Small, early stage caterpillar of Papilio polyxenes coloro, probably a second instar, on host Thamnosma montana. April 15, 2011, at the Cactus Springs Trail in the Santa Rosa Wilderness.
'Desert' Black Swallowtail - Papilio polyxenes coloro
Another caterpillar of Papilio polyxenes coloro, probably a fourth instar. After this stage, the spines disappear and they become smooth - see the one above from 2017. April 30, 2019, again at Cactus Springs Trail in the Santa Rosa Wilderness.
'Desert' Black Swallowtail - Papilio polyxenes coloro black form
I chased this black coloro all over the desert floor off Lanfair Road on the way to a hike in the New York Mountains in the Mojave National Preserve. John Comstock named the dark forms clarki and comstocki that pop up rarely in desert swallowtails, and this one would appear to be the former (no pun intended). Taxonomically, that means next to nothing; it's just a cool aberration.

©Dennis Walker