If you hiked to the summit of Lassen Peak in the Fall, you were probably one of the lucky visitors to encounter millions of California Tortoiseshell Butterflies. They ride the warm air currents up into the lunar terrain of the young volcanic crater.
Nymphalis californica are a winter-hibernating species — in California, most often in the Central Valley or Inner Coast range. During summer months, they undertake a seasonal migration — often traveling to the higher elevations of the Klamaths, Sierra Nevada, and the Cascades. Their larva feed almost exclusively on species of Ceanothus and occasionally massive population booms can occur, resulting in near-epic numbers in migratory groups, making an amazing viewing party for hikers. See for yourself:
Make sure you schedule your hike to the top of Lassen Peak next fall to see this incredible event!