As promised, photo comparison for your information.
Please note that the E. subcinerea illustrated here is the more typical "burnt" form (and has no white apical mark).
Key points to help differentiate the species:
E. acutangula - very abruptly angled mid-termen on both fore and hind wings; a double medial band on dorsal wing surface; very dark; forewing much narrower than congeners.
E. inangulata - two small white points in discal area of forewing on dorsal surface; very rounded termen on hindwing; forewing as broad as E. fraterna; two dark blotches in discal cell below costa on ventral surface of forewing (c.f. one blotch in E. fraterna). Median fascia on forewing (both dorsal and ventral surfaces) meets the costa acutely (c.f. E. fraterna).
E. subcinerea - ventral surface looks burnt - high contrast between terminal (pale) and subterminal (dark) zones. Note: dorsal pattern variable (can look like the specimens of E. fraterna or E. pertendens in the photo below).
E. pertendens - forewing shape not quite as narrow or angled as E. acutangula; ventral pattern pale (c.f. E. subcinerea), with only the median fascia prominent. Note - dorsal pattern variable (can look like the specimens of E. fraterna or E. subcinerea in the photo below).
E. fraterna - broadest wings of all; hindwing termen not as rounded as E. inangulata and the two white points in discal area of forewing on dorsal surface less prominent than in E. inangulata, or absent. Median fascia on forewing (both dorsal and ventral surfaces) meets the costa at right angles (c.f. E. inangulata).
Hope this helps!
[ Last edited by hkmoths at 2013-10-17 22:18 ]
[difficult to identify Ericeia spp. (Noctuidae) from Hong Kong]