by GasMacc1 on Wed Sep 15, 2021 9:55 am
The standard wording in more than one text book is:
"Males can be easily distinguished from both sexes of E. gentianaeana and E. oblongana by their white hindwings. Both sexes can be seperated from E. gentianaeana by the narrower area of whitish ground colour distad of the median fascia. Some specimens, especially females, may need retaining".
That would seem to suggest that a hindwing check would be required, but would only lead to a confirmed ID if the specimen was male. If your moth was female, you could use the photos to separate from E. gentianeana, but not from E. oblongana.
Previous records of E. marginana in Cheshire have either been supported by a hindwing check or by gen. det.