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Hi Dr Seow,
I made a few images that point out the ID features for the Six Line Nacadubas and also a couple of easily mistaken species. Could you take a look and see if I missed out any important features? Thank you!
1. Nacaduba berenice
Attachment 28187
2. Nacaduba kurava
Attachment 28188
3. Nacaduba calauria
Attachment 28189
4. Nacaduba beroe
Attachment 28190
5. Ionolyce helicon
Attachment 28191
6. Prosotas aluta
Attachment 28192
1. N. berenice.Dark striae strong in both sexes.
The submarginal spots are broadly & irregularly lunulate(moon-shaped)or chevrons (V-shaped).
Sagitate is arrowhead shape.
https://sweetgum.nybg.org/images3/341/913/Sagittate.jpg
The submarginal spots in Tanaecia pelea are sagittate.
https://inaturalist-open-data.s3.ama...0640/large.jpg
Female UpF patch pale lavender blue.
2. N kurava. Dark striae somewhat weak in the male.
Male with straight termen (outer margin),
Male upperside violet blue with underside markings visible by transparency.
https://2.bp.blogspot.com/-eyI8J8P5M...eBlueCombo.jpg
http://www.butterflycircle.com/check...ze%20Siong.jpg
Female UpF patch pale blue & apically whitened.
https://upload.wikimedia.org/wikiped...w_20150718.jpg
3. N. calauria. Dark striae strong in both sexes.
Female upF patch violet blue.
4. N. beroe.
Male with the dark striae weak & may be partially obsolete.
Wingbase darkened in the male.
Female UpF patch violet blue with bluish white submarginal spots.
5. Ionolyce helicon.
Not sure if the sub-basal bar is relevant.
6. Prosotas aluta.
Submarginal spots are not sagittate, but roughly lunulate.
FW postdiscal is usually described as dislocated at vein 4, with the lowest spot (in space 3, ie spot 3) shifted inwards.
Note; The space you marked as space 3 is actually space 4. Count the spaces from bottom up, ie. space 1b, space 2, 3, & 4.
TL Seow: Cheers,
Thank you Dr Seow for the corrections, especially the correct phrasing for the submarginal spots! I wanted to make it easier for more people to ID the Nacadubas and chose the more prominent features, since usually the uppersides aren't as easily observed, I did not put much emphasis on that. The darkness of the striae can be rather subjective and for less experienced shooters may be difficult to judge. Also the sub-basal bar in Ionolyce helicon was just an additional feature to differentiate it from Prosotas aluta, as some individuals do end up looking very alike, but I guess it could be omitted.
There is still a lot of confusion particularly in identifying the female.
All females have the UpF ground colour dark brown with a blue patch.
Just seeing a bit of dark marginal area of the FW does not equate it to calauria.
The colouring of the upperside of the males of berenice & calauria are often confused.
The upperside of the berenice male is a pale frosted blue, but can be somewhat brilliant in a side light.
N. berenice males.
http://2.bp.blogspot.com/-2z1tHnAAtb...8male%2529.jpg
https://inaturalist-open-data.s3.ama...9/original.jpg
https://inaturalist-open-data.s3.ama...0768/large.jpg
The upperside male of N. calauria is a deep darkish violet ,as seen in these three males.
https://wanderingbutterflyeffect.fil...b3ad98860e.jpg
https://inaturalist-open-data.s3.ama...644/large.jpeg
https://inaturalist-open-data.s3.ama.../original.jpeg
Finally this is a misidentification & is a berenice male. (set specimen.)
https://singapore.biodiversity.onlin...doptera-000141
And this a berenice female.
https://singapore.biodiversity.onlin...doptera-000139
TL Seow: Cheers.
PS> Typical N. beroe male. Note dark striae are very weak.
http://www.butterflycircle.com/check...lt_male_01.jpg