Quote Originally Posted by Psyche View Post
This is one of those enigma in Singapore that have never been solved.
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The only way to find out if there are two species is to catch a male with a defined white spot.
Squeezing the abdom,en will cause the valves to open out.
A smartphone picture of the inside of one of the valve, zoomed for comparison.
https://yutaka.it-n.jp/lyc4f/81900001.html
https://yutaka.it-n.jp/lyc4f/81920010.html

TL Seow: Cheers.
Many thanks, Dr Seow for the detailed explanation.
From CP4, the difference in the male valva is about being unilobate (A. norda) or bilobate (A. major). The links at yutaka.it-n.jp show the difference clearly.
Definitely more work is needed in order to solve this SG mystery.