California Tortoiseshell (Nymphalis californica): The brightly colored dorsal (upper) side of the wings is opposite to their ventral (under) side, which looks more like a dead leaf. These amazing butterflies are among the first butterflies we see in the late winter / early spring (as early as March). The new generation emerges in late July and August here in MT. They do a short “summer hibernation” soon after emerging and become active again in the late summer and fall. They will then head into their winter hibernation and begin flying once the weather warms up in March or April. This individual butterfly can therefore have a lifespan of 9 to 10 months. 

Milbert’s Tortoiseshell (Aglais milberti): The Milbert’s Tortoiseshell is closely related to the California Tortoiseshell but they are smaller and differ in coloration, as you can see from the photo, and their range is much larger in the US and Canada. They too remain inactive for lengthy periods in summer and overwinter as adults.
Photo by Glenn Marangelo on 3/22/20 in Missoula, MT.