Drepanosticta revisited - a new species after all*

*This entry adjusted August 8, 2018. The new species described below has been published by Dow & Kompier (2018) as Drepanosticta emtrai.

Today, June 27, I had a home day, during my 3 week survey of Northern Vietnam. But of course I could not stay in, so I went for a short trip to Hoa Binh Province, to a touristic site Sebastien introduced to me. Sorry to say, I hated it, but while I was there I noticed a female Coeliccia that was big and had the colors of C. uenoi. That would be a great discovery, so I looked around for the male. I did not find it. But while doing so, I noticed a Drepanosticta. It looked as it was supposed, dark thorax, small rings on dark abdomen, blue abdomen tip. All the works of D. hongkongensis, see the other blog entry on that species. Nevertheless, in hand the appendages appeared different and because it was a new location, I ventured to take it with me. Ba Vi is of course not that far from Hoa Binh, but far enough. When I got home I checked it under the microscope and lo and behold! It showed the same lobe on the superior appendage as the specimen from Ba Vi I took pictures of last year and now, after seeing a great many D. hongkongensis, had sort of dismissed as aberrant (see the first Drepanosticta entry). There are in fact many differences in the appendages, apart from its slightly smaller size, and like I thought of last year's specimen, it has blue markings on the prothorax and also a small blue mark at the base of the second pair of wings. There can be no doubt, this is a different Drepanosticta species and the same as that encountered last year on Ba Vi mountain. Clearly, there are two species in that forest, possibly one appearing earlier (May) and the other later (June/July)!

The two species side by side. On top is Drepanosticta hongkongensis, albeit larger than originally described by Wilson and with pale anterior lobe to the prothorax. In this scan a preserved specimen was used for comparison, so it is slightly duller than in real life. The bottom specimen is the new species from Hoa Binh. It is marginally smaller.

Appendages of D. hongkongensis in dorsal view. Note the blunt tooth to the inferiors.

The same for the new species, note the acute tooth, slanted posteriorly.

Ventral view of appendages of D. hongkongensis. Note the blunt tooth to the inferiors and absence in this view of a process to the superiors (which in fact have a small process, as can be seen in dorsolateral view).

The rather differently shaped appendages of the new species (Drepanosticta emtrai). Dorsum of superiors smoothly rounded and large ventral process at 3/4th of length of superiors.

In dorsolateral view a small process can be seen in D. hongkongensis on the inside of the superior appendages.

This is clearly much more prominent in the new species (Drepanosticta emtrai)

Ventral view of appendages of D. hongkongensis. Note almost straight outer edge of inferiors, that smoothly bend inwards towards the tip.

This is very different in Drepanosticta emtrai. At the halfway point (where the acute tooth can be seen) the appendages make a clear bend outwards and curve almost semicircular back inwards again.

The prothorax shows blue on the lateral lobes and on the anterior lobe.

Here in view of the complete thorax blue can also be seen at the bases of the wings, notably the second pair.

Eventful day at Tay Thien, a few more goodies

This weekend (June 15-16) proved pretty productive at Tay Thien. Apart from the species already described, I encountered about 50 more. Here are a few other highlights

The first was this beautify male Polycanthagyna erythromelas. I saw several females flying about, but this male resting for a short while in a nearby bush was a treat.

And in the lower river stretches were several Lamelligomphus formosanus active. Once you know the species, it is not so confusing anymore.

Another species present in good numbers, towards the evening in the open and during the day in dark clearings, was Macromidia rapida. I was lucky with a male that perched nearby.

The female of Sinorogomphus sachiyoae. Very much like the male in appearance. After these shots she happily continued ovipositing.

Another cool female, Heliogomphus scorpio. The male was active nearby as she was ovipositing near the nunnery. Like the male, very pale (white) metepimeron, unlike Heliogomphus sp., which occurred at the same stretch, but is much yellower.

Here a close-up of her pretty face. Note the horn on the occipital ridge.

There was something else I did not expect, Drepanosticta hongkongensis. I noticed a male at 350m asl beyond the nunnery. Under the microscope it is identical to the specimens from Ba Vi. I thought the species there was known only from that location in Vietnam, but when this is D. hongkongensis, well, in that case it is not surprising it occurs elsewhere. Although the caudal appendages are identical, the anterior lobe of the prothorax is all black, as it should be for D. hongkongensis, unlike the specimens from Ba Vi.

The penile organ, identical

As are the caudal appendages

Drepanosticta hongkongensis

May 25 I went to Ba Vi to look for the promising Drepanosticta there. I reported on it last year, when I saw them in May on a visit to Vietnam and found only one male in July after we moved here. Based on the close-ups of that time I wrote that surely this was an unidentified species. Indeed, looking at the photos, it is uncanny to see the lobe on the superior appendage, which does not fit closely allied species. But on the 25th I saw several males and also looked at them in close-up. I am sure it is the same species as I saw last year, but none had the lobe! Which pointed me straightaway to D. brownelli or D. hongkongensis. (I do not know why the specimen last year was different, some defect or damage? Also, at the time I described blue on the pronotum. Again, no sign of that now.) Keith Wilson has published on both species and pointed out the differences between them. In the appendages these are virtually absent and also the penile organ is difficult to use for identification. I found the flagella rather variable in the small sample I looked at, so I worry about the usefulness of that character. Brownelli has pale anterior lobe to the prothorax and abdomen is 37-43 mm, hongkongensis has blackish anterior lobe and has abdomen 31-36 mm. The Ba Vi specimens are about 39mm in abdominal length and has cream-white anterior lobe. This seems a clear case of D. brownelli. However, segments 8-10 in brownelli have grayish white dorsum, in hongkongensis bright cyan blue. Hey, the Ba Vi specimen are also bright blue. Nevertheless, I would say that just the color of the dorsum of S8-10 is a little to go by to claim it as a different species. because of this, I considered it D. brownelli. Keith Wilson however commented as follows:

"Colour and size are not always reliable characters in establishing a species’ taxonomic status but in the case of Drepanosticta brownelli and Drepanosticta hongkongensis both are useful aids. D. brownelli is a relatively large species, with male abdomen and caudal appendages ranging from 37-42 mm as compared to the smaller D. hongkongensis which ranges from 31-36 mm. The dorsum of D. brownelli’s abdominal segments 8-10 are predominantly coloured very pale whitish-blue or pale greyish-white whereas the caudal, dorsal patches of D. hongkongensis are colured bright cyan blue. The distinguishing morphological feature is the acutely reflexed horn-like processes of the penile organ found in D. brownelli, (best viewed laterally),  contrasting with the smoothly curved horn-like processes of D. hongkongensis [see Wilson, 1997: The Platystictidae of Hong Kong and Guangdong, with descriptions of a new genus and two new species (Zygoptera). Odonatologica 21(1): 59-63]. The colour and shape of the penile organ in your photos indicate D. hongkongensis."

Drepanosticta hongkongensis, male. Note that due to flash the dorsum of S8-10 is lighter than in reality. The white on the thorax is some kind of defect.

Another male, abdomen tip lighter than in real life

Appendages in dorsal view

In dorso-lateral view

In lateral view

And in ventro-lateral view

Penis in lateral view

In ventral view

Close-up showing cream anterior lobe of prothorax

Drepanosticta sp.

This summer, just after arriving in Vietnam, we went to Ba Vi. I had already visited the mountain in May and seen some Drepanosticta damsels and now back in Vietnam was ready to go and clinch their ID. Sadly, there were not many around, in fact on July 13 I saw only one. Maybe it is a spring species. Anyway, as it kept to the shade, I could only make a record shot and with the flash, the blue on the abdominal tip looks whitish. As you can see from the close-up, it is actually really blue. The close-up also shows the shape of the appendages. There are several species that have rather similar appendages and, to some extent, coloration. These are D. vietnamica, which has a dorsal process on the upper appendages, and a lateral stripe on the synthorax, D. brownelli and D. hongkongensis, which both have smoother appendages without the obvious inner lobe about 1/3 from the tip. Both also have the prothorax either dark with lighter anterior edge, or all dark, whereas the species from Ba Vi (not clear in these pictures) has a clear straight blue line along the anterior edge of the pronotum and a blue anterior lobe. Also, D. brownelli has whitish abdominal tip. Although clearly closely related, the Ba Vi species appears to be something else. Next spring, time to collect and describe.

Drepanosticta sp., male. Due to the flash abdominal tip not as blue as in normal light.

Appendages, showing inferiors tapering into an acute point and superiors with large lobe on the internal side.