Powell and Opler (2009) state
Nadata oregonensis is similar to
Nadata gibbosa but the forewing has a yellowish patch in the discal cell and the postmedian line curves slightly basal at the inner margin. (
This is not a reliable diagnostic feature.) The forewing of
N. oregonensis appears more blotchy.
(1)
Nadata gibbosa, the postmedian line does not curve basally at inner margin. (
This is contradicted by MONA Fascicle 22.1A (2) which shows 6 spread specimens of oregonensis, none of which show a pm. line curving basally at the inner margin and several gibbosa which do to varying degrees.)
Hypothetical: Throughout the range of
N. gibbosa, on barcoded examples illustrated on BOLD, the white reniform dots are invariably round or only slightly oval. On the few examples of
N. oregonensis on BOLD and many images in the California range of the genus (many presumed to be
oregonensis), one or both white reniform dots are elongated perpendicular to the costa, showing more as a "comma" mark than a circular dot. This distinction is evident in most of the spread examples of
oregonensis illustrated in the recent MONA fascicle.
(2) This potential distinction (i.e., IF a moth has comma-shaped dots, it is
oregonensis) needs further investigation on adults confirmed by genitalic examination and/or barcoding.