Moved from Butterflies and Moths.

From iNaturalist:
“Btw, for distinction between the two similar Euchromius species, I follow the explanation given at https://www.inaturalist.org/observations/92982640 and illustrated in the 2nd photo there. I hope it is correct.”

This is a comment within above link:
“After-hours permit graciously provided by the California Department of Fish and Wildlife.
The second picture presents a direct side-by-side comparison of E. californicalis and E. ocellea (3 individuals each; all observed at the same place and night) as I currently understand it. The main difference is the location of the dark line (marked by a red arrow in the top photos) within the surrounding white field. (Please, note though that there is no guarantee for this to work, and there seem to be counterexamples on BOLD.)
Based on this ID method, I have found E. californicalis only in one small area (Yolo Bypass) where others also have seen it. In contrast, E. ocellea is much more broadly distributed.”