Common in both the Coast Range and Sierra foothills, to 5000'; absent at Donner and Castle Peak; common in Sierra Valley; absent from the Sacramento Valley and Suisun. Populations in the Coast Range have mostly black larvae with orange markings and little if any white. Populations from the lower foothills (beginning at Sailor Bar, Fair Oaks, Sacramento Co.) eastward have strong lengthwise white larval striping.

This colonial species is divided into numerous taxonomic subspecies. Since none of our populations belongs to a legally-protected subspecies, we will ignore the trinomials here. Much more local than E. chalcedona, usually flying earlier, and in our area easily told from it by the rounded wings, reduced black above, lack of white spots on abdomen, and partly-black antennal club. Many populations occur on serpentine. On our transect the only population west of the Sierran crest is at Washington.