This is one of the very few butterflies adapted to climax Red Fir forest. It can be abundant at Donner and Castle Peak (below tree-line only), where males pack onto mud puddles along trails early in the season. Adults visit Aster, Pink Pussy-Paws, Coyotemint, etc. and remain in the sun, although surrounded by the fir canopy. There is considerable minor pattern variation.

A common species of the Southwest deserts which somehow became briefly established in North Sacramento in the early 1970s (a couple of records also in West Sacramento, across the river) but died out quickly; it is not properly part of our fauna. It is extremely variable phenotypically. Multiple broods; host plants Sunflowers (Helianthus), including H. annuus in our area.

Common in the foothills and to 7000', but only a rare stray in the Central Valley. Males are territorial perchers, often in paths or on rocks. Where Euphydryas chalcedona (q.v.) is strongly blackish, the females of the Northern Checkerspot are trimorphic - orange and male-like, black with yellow spots (an apparent mimic of E. chalcedona), and intermediate. Where E. chalcedona is mostly red, only the male-like female morph occurs (true also at Donner, where there are no chalcedona).