Atlides halesus corcorani
Great Purple Hairstreak
Large - for a hairstreak - and featuring brilliant metallic blue, light green, red and orange set against black. The white spots against the black of the head and thorax remind one of a monarch's coloration. Atlides halesus corcorani is a spectacular member of a tropical group of butterflies that is like nothing else in southern California. Other members of the genus Atlides - there are about 17 - are more or less similar to halesus, but only the latter ranges north into the U.S. Not particularly rare, it uses many species of mistletoe and can be found in a variety of places, but it's always a head-turner when spotted. I've seen it sporatically in places such as Big Rock Creek in the San Gabriels in the fall; along Cactus Spring Trail (not reliably) in spring; and Anza-Borrego (Plum Canyon, also spring).
In the deserts around Junipers, look for Phoradendron densum and there's a chance the butterfly will be in the area, perhaps on flowers nectaring. Where mesquite, catclaw, etc. grow, the mistletoe will probably be Phoradendron californicum. Another is Phoradendron macrophyllum, on Cottonwood, Willow and Sycamore trees. It flies much of the year.
This male Atlides halesus corcorani was nectaring on California Buckwheat on June 3, 2017 at Cactus Spring Trail.
Male Great Purple Hairstreak, Atlides halesus corcorani, surely one our most exotic-looking butterflies in California. This one was nectaring on Desert Lavendar in Plum Canyon, Anza-Borrego Desert State Park. October 3, 2005. Males have blue scaling on the ventral forewing, barely visible here, that females lack.
I found this one roadside in the Valyermo area, where the desert meets the San Gabriel Mountains. September 11, 2008. The roadsides there are good places to look for this species.
Female Great Purple Hairstreak from Arizona - Boyce Thompson Arboretum, September 25, 2007. Note the lack of blue scales on the forewing.
Another female. This time, I was on Kelbaker Road in the Mojave National Reserve near Granite Pass. October 7, 2019.
The hostplants for Atlides halesus corcorani are species of mistletoe. This is Phoradendron californicum on what looks like Mesquite in Anza-Borrego. March 1, 2009.
Here's a look at another host plant for this hairstreak: Phoradendron densum, which parasitizes junipers and cypresses (California Juniper in this instance).
I spotted this little Phoradendron densum near the top of this juniper along Cactus Spring Trail, and checked it for eggs of Atlides halesus corcorani - see below.
And here is an egg of Atlides halesus corcorani on a leaf of that Phoradendron densum above. May 27, 2016.