Tuesday, 28 October 2014

Planaeschna - just when it started to make sense

Planaeshnids are beautiful, generally slender and brightly patterned Aeshnids. They are also notoriously difficult to separate. What is more, some characteristics are difficult to ascertain. As I tried to point out, drawings of the penile organs depend on the state of the specimen. That is not to say the shape is of no meaning. Far from it. There are also subtle differences in markings between similar species. Then there are small differences in the appendages, but it seems that many species have largely similar appendages. Thus a combination of minor differences may point the way to specific identification. Then there are many species and maybe many more awaiting description, but also there may well be several names that are synonyms referring to the same species. It does not help that many species are described based on just one of a few types and rarely recorded. Good photographs are generally lacking and with the slight differences in patterning and shape the quality of drawings is of great influence. And thus with 4 species bagged this Sunday in Xuan Son I knew there would be no end to my troubles. Today I will start with the easy species. Planaeschna gressitti. After Sebastien found it this spring on Mau Son in Lang Son Province I have also found it at Pia Oac. There are hardly any differences between specimens of the two locations. I already noted that it is somewhat worrying that very similar P. tamdaoensis was recorded from the same altitude somewhere in between these locations. Going back to the literature I found that P. suichangensis was in fact also extremely similar. Wilson (2005) points out that differences between P. tamdaoensis and P. suichangensis are slight and that the former may be a junior synonym of the latter. Problem is that although Wilson gives good drawings of both the dorsal view and patterning of the abdomen and lateral of the first few segments, this is not so in Asahina (1996) or Karube (2002). This somewhat complicates comparison. Now, the patterning on S1-3 is a close match especially with P. suichangensis as depicted in Wilson. The pale line on the dorsum of S3 or the dorsal patterning of S1-2 and the lateral patterning on these same segments is identical. The dorsal or ventral view of the appendages is somewhat paddle shaped, clearly broadened in the apical half. This is also a good match, but this is the same for P. tamdaoensis or P. gressitti. The angle of the superior appendages in lateral view is the largest difference between these species, with P. gressitti being the straightest and P. tamdaoensis the most sinuous. The facial patterning of all these species is depicted as characterized by an all black antefrons.
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. 1 face. As you can see the yellow area on the labrum is heavily bordered black and split in the middle by a black line. The anteclypeus is very dark blackish brown and the antefrons has no lower yellow border and the yellow sides do not extend towards the antennae. See the posts on P. gressitti for the facial view of the species.
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
Although extremely similar in patterning, it is clear from the shape of the appendages and the facial pattern that this is most likely a different species. But the undulating outline of the appendages in dorsal view is different from P. tamdaoensis, P. gressitti and P. suichangensis. So what is it?

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