Hidden in the hills of the East Bay Area, an elusive and rare butterfly is making a comeback. Published by Bay Nature.
The Sonoran Blue is, according to some experts, the most beautiful butterfly in the Bay Area. Alum Rock Park in San Jose is the best place to find them, and even here it’s not easy. “We like the blues since they’re difficult,” lepidopterist Bill Shepherd tells me. “They’re on the hills that crumble under your feet as you try to get a closer look, they’re small, and you never know quite what to expect.”
There are several species of blue butterflies in the Bay Area. Catching a glimpse of the bright Sonoran, I understood why we had spent so much time and energy looking for one tiny creature. Unlike their counterparts, Sonorans sport brilliant red-orange spots on the forewing and a brilliant blue shine. In females, matching red spots adorn the hindwing as well. Like many species, males actively patrol for females throughout their short lifespan. They float over craggy outcroppings, banks, and cliffs with their tell-tale weak flight. Males can often be spotted floating down a sloped hill in the hopes of finding a mate, only to rise back up and meander down the slope again.
Place is of utmost importance to the Sonoran blue, as its populations rarely travel to other areas. Extremely local, it is found only in specific pockets in the Bay and south along the coast to Baja. (A subspecies in the upper San Gabriel River went extinct when its home was destroyed in 1969, showing just how vulnerable the butterflies are to habitat destruction.) The Sonoran blue’s distinct colonies led to the rapid creation of “ecotypes” specifically evolved for particular environments. These ecotypes specialize on native host plants and ultimately may form distinct species. This process continually raises new challenges to the identification and classification of the plethora of butterflies in the Bay Area.