Now, the specimens from Pia Oac and Mau Son are similar in these respects, but also characterized by a clear yellow lower border to the antefrons. The sides are also yellow and this moves up high towards the apex. They share the pale line of the dorsum of S3, have slim lines almost touching centrally on S2 forming a cross, and paddle shaped appendages. In these respects they are very similar, but they differ from the drawings of all three species concerned in the yellow lower border to the antefrons.
Now let's consider the very similar species of Xuan Son, a location much lower (450m asl). My first impression was that this too is M. gressitti (if that is what the others are). But they do not have a lower yellow margin to the black antefrons. Also, the labrum is bordered by an even blacker anteclypeus and has not only black borders, but the yellow is split in the center into two distinct yellow spots. The yellow on the sides of the antefrons also does not extend as far towards the apex. The appendages are not as paddle shaped at all. And the pattern on S1-3 is different too. The cross on S1-2 is more robust, but also more separated, and S3 misses the dorsal line. It is possible that these are regional differences and little is known about the variation, either geographically or within populations, but the two males I caught at Xuan Son are highly similar to each other and so where the different specimens of Pia Oac and Mau Son, but of course not to those from Xuan Son.
|Male Planaeschna with black and yellow face from Xuan Son No. 1|
|Male No. 2|
|Male No. 2 face, very similar, but even dark on anteclypeus|
|Dorsal view of specimen from Mau Son. Note the dorsal line on S3 and the cross on S2.|
|Dorsal view of specimen from Pia Oac. Very similar|
|Dorsal view of No. 1 male from Xuan Son, note lack of dorsal line and robust but open cross on S2|
|Dorsal view of No. 2 male, very similar|
|The appendages of the Mau Son specimen in dorsal view|
|The same in lateral view|
|No. 1 from Xuan Son, undulating and not as paddle shaped|
|In lateral view one smooth broad curve, not sinuous|
|No. 2 male exactly the same differences|
|Indeed, smooth broad curve of male No. 2|