A very distinctive and charismatic butterfly, best known for its conspicuous activity in late winter, flying and acting territorial before any trees have leafed out or any wildflowers are active. It hibernates as an adult. In the Sacramento Valley there appears to be only one brood (in spring); the resulting adults migrate upslope and breed in the mountains. There is a reverse downslope migration by the next generation, in late September-October.

Along with the Painted Lady, this is a mass migrant that makes news at irregular intervals by tying up traffic! The "Tortie" overwinters as an adult and can sometimes be seen sunning itself in midwinter on mild days. It is generally common in foothill canyons in late winter, ovipositing on the young, tender growth of various species of Wild Lilac (Ceanothus). The spiny, black-marked-with-yellow larvae feed gregariously, without a web, and in big years can defoliate whole stands of the plants.

Recorded from most sites on the transect, but this is an altitudinal migrant that spends the winter as an adult near sea level, breeds there in spring, then shifts to the Sierra (particularly the East slope) for summer breeding before returning west in autumn. Fresh adults are often common on Coyotemint at tree-line on Castle Peak, even though there are no host plants that high. They were apparently born and bred on stinging nettle (Urtica holosericea) around Truckee and Loyalton!