Two bright orange butterflies flew into my yard this week between the rain storms. I snapped a photo and determined they were Gulf fritillary (Agraulis vanillae) butterflies. These low-flying, bright orange butterflies have beautiful silver spots on their underwing.
According to Butterflies through Binoculars: The West, Sonoma County is at the northern end of their range, although they are increasing in coastal California (see this 2009 UC Davis article about their historic range and how they have returned to Sacramento and Davis). Their range extends all the way to central Argentina.
Gulf fritillary butterflies have wingspans up to 4 inches and like yards and gardens, open woodlands and thorn scrub. The caterpillars feed on passion-flower. They are mainly seen from May-October.
According to the UC Davis article: “Adults live for several weeks and breeding occurs year-round. As a tropical species, this butterfly has no true winter dormancy and will be eradicated if the temperature falls to about 22F. It has managed to survive several severe freezes in the Bay Area, but must be regarded as in constant jeopardy of being frozen out of its Central Valley outposts.”
For some great photos of adults and caterpillars, check out this Natural History of Orange County website.