Philoganga revisited - the case for several species

*Text slightly adjusted on August 19, 2019. The reference to P. robusta being sometimes pruinose may be mistaken, it could just as well be P. vetusta. The species incertae in fact is P. montana and has been recorded also in 2018 in Cao Bang (male and female).

I already posted in the past on Philoganga. At the time I discussed the occurrence of whiter specimens presumably P. robusta, if we consider that the colour pattern of the specimens is a reliable indicator of specific identity.

This spring I noticed in early May that Philoganga were quite common on Mau Son mountain in Lang Son Province. The thing was that they were consistently pale bluish-green on the abdomen and none where orange. This triggered me in collecting more Philoganga this year for comparison. Although sample size is still small, it supports the impression in the field from larger numbers of specimens that Mau Son specimens were larger and more robust on average than P. vetusta.

The issue is complicated, because older males seem to sometimes develop pruinosity that makes them appear whitish. This has not been established amongst the population of P. robusta of Mau Son. There is also some variability in size of specimens, especially, it would seem, in P. vestusta.

Wilson & Reels (2001) reviewed the literature on Chinese records of Philoganga. There is no need to repeat here their excellent overview of mistakes and inconsistencies in the records of these very similar species. What they did conclude was that some characteristics mentioned in the literature to separate the species were clearly erroneous. The number of cells in between the wing margin and 1A is such a character. Indeed, I could find no consistent difference between what I consider P. vetusta and P. robusta in this character.

Wilson & Reels do suggest that the presence or absence of an antehumeral stripe could be of help. I found that the antehumeral may be somewhat more prominent in P. robusta, but that it can also be prominent in P. vetusta. Prominence seems to be related to age, with older specimens becoming darker on the dorsum of the synthorax with reduced or faded antehumeral.

The number of antenodal cross veins has also been mentioned as possible identification character. This was already pointed out by Wilson & Reels as invalid. Indeed, I counted 12-14 antenodals in definite P. vetusta (N=4) and 13-15 in P. robusta (N=3). Likewise postnodals range from 30-31 in P. vetusta to 29-34 in P. robusta. I have found no differences either for the few females I collected, but it is hard to draw conclusions, as the specific identity is difficult to prove, although one was caught in tandem with P. vetusta male and thus presumably that species

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Wilson & Reels mentions that abdomen size of specimens from Hainan for P. robusta was 61.0 mm. My specimens are slightly smaller, 56-58.5 mm. They are however clearly larger than the bright orange typical P. vetusta that I was able to collect, which ranged from 51-54mm. I plotted the sizes in a graph replicated below.

Chart 1. Four definite P. vetusta from Xuan Son and two definite P. robusta from Mau Son are plotted by size (abdomen incl appendages versus hind wing length). Red crosses refer to two pruinose specimens, both from Xuan Son. The largest appears by colour to be P. robusta, the other could be either. Green squares refer to one teneral specimen from Tam Dao, possibly P. robusta, and one to Philoganga species incertae, see main text. Thus although non-pruinose whitish specimens appear to be constantly larger than orange specimens (but beware of sample size) there is a small area of overlap.

It thus seems that the hypothesis that P. robusta can be identified by colour alone from P. vetusta is supported by the measurements of the specimens involved. Nevertheless more specimens are needed and from different areas to substantiate this. After all, local populations may be genetically homogeneous, which may influence the size distribution.

In the graph a single Philoganga species incertae is represented by one of the green squares. This specimen was caught in Cao Bang Province close to Cao Bang city on May 20. From its size it seemed to fit P. vetusta. However, the dorsum of S1-4 is black, not even whitish. It has a cream bar over the cranium of the head, which is absent in either P. vetusta and P. robusta when mature, although this may be an indication that the present specimen is still immature. In fact at first I dismissed it as just that, an immature P. vetusta. However, as can be seen from the pictures below, it has two strange characteristics in its wing I have not seen in any other Philoganga. The most striking is that vein 1A seems to run on further than in other species, where it curves back to the wing margin. Therefore even at the wing margin there is only one row of cells between 1A and CuP, whereas in P. robusta and P. vetusta there is a whole field of easily 10 cells. Furthermore the quadrangle is much more square than the elongated quadrangles of either P. robusta and P. vetusta. These aspects indicate the possibility of this being in fact an unknown species of Philoganga.

Two males Philoganga robusta from Mau Son and what is presumably a female of the same species. Note the blueish-green colour of S1-4, although the smallest specimen also has a hint of orange.

The same three specimens in lateral view. They are not pruinose, but the males lack orange on the thorax or first abdominal segments.

Three typical P. vetusta males from Xuan Son, displaying bright orange abdomen and varying degrees of clarity of the antehumeral stripe. The top right specimen is similar in size, but has pruinosity covering the first few abdominal segments and sides of thorax. It is difficult to say whether this is vetusta or a small robusta.

Typical P. vetusta male caught in tandem with female. Pattern of dorsum of S9 of female is different from possible female P. robusta. However, this female is the larger of the two, 72mm total body length against 67mm for the Mau Son female.

The same specimens in lateral view, the male displaying bright orange both on the thorax and on the first abdominal segments.

Aged specimens from Xuan Son. Top male P. vetusta showing that aged individuals at least not always covered in pruinosity. Below very large aged specimen with pruinosity on the thorax, but very dull abdomen, tentatively identified as P. robusta on combination of size and lack of bright orange.

Philoganga species incertae. Note the wing pattern with absence of a field between 1A and CuP,  which is very different from the wing pattern of specimens illustrated above. Note also bar over cranium.

Hind wing detail of Philoganga vetusta, showing 10 cells between location where 1A reaches the wing margin and location where CuP reaches wing margin and field at widest location 3 cells wide. 

Hind wing detail of Philoganga species incertae, displaying three cells only between 1A and CuP, and field, if you can call it that, 1 cell wide. Apologies for the legend (A1 versus 1A)

Philoganga robusta

The genus Philoganga is represented in northern Vietnam by the magnificent Philoganga vetusta, the Ochre Titan. This species characteristically develops bright orange-red dorsum to the first segments of the abdomen and to the flanks of the synthorax. In southern China there are two species. Next to the Ochre Titan, there is another species, Philoganga robusta. Wilson and Reels reviewed many of the records and looked at many specimens and concluded that the structural differences between these two species are difficult to ascertain and inconsistent. However, life insects are easily separated because, as they write (2003): The differences between vetusta and robusta are relatively minor and non-structural in nature. Nevertheless life male specimens are easily separated in the field since robusta is predominantly dark colored with greenish blue markings, whereas vetusta is extensively marked with bright orange on the thorax and abdomen. Now, already in Tam Dao both Sebastien and myself encountered a large whitish Philoganga without any orange. However, the dorsum of the abdomen of this insect was not dark, and showed also some orange (see that post). We considered it maybe an aberration. However, on June 23 I encountered a male in Pia Oac Nature Reserve that displayed the typical coloration of P. robusta. If lack of structural characteristics, but color is the identifying feature, there should be no objection to identifying this specimen as P. robusta. More research may be needed and copula looked for, but until then we should assume that just as in southern China, both species occur in northern Vietnam. The other option is that these are in fact two forms of the same species, in which case P. vetusta is the  senior synonym.

Note the dark dorsum, especially noticeable on S2, whitish flanks marked with blueish. The legs appear to have some orange.

Philoganga vetusta - the big, the bold, the beautiful

When I first noticed the Ochre Titan in Tam Dao I was shocked by its robustness. This is a very large damsel and very strongly built. I ran into it again in Xuan Son and apparently it is not all that rare in spring. On 17 and 18 May I saw them in Tam Dao from low down up to 350m asl in good numbers, meaning at least 15 or so. Here are a few shots.

The mature male, with extensive orange to the abdomen and ochre to the flanks.

The massive female, sometimes whitish, sometimes ochre

And another male, maybe immature? The wings look old and worn. Is this pruinosity and this in fact a very mature specimen?

En route to Sapa, Xuan Son

*Update 24 December 2022: the Protosticta grandis of Xuan Son may be a different species from the known "grandis" types. It is certainly not P. grandis sensu Asahina.

Between April 12 and April 18 we travelled to Xuan Son, on to Sapa, back along route 32 to Ba Vi and finally home to Hanoi. As I was showing birding pal Hein around, it was a birding trip, but I did manage to keep an eye open for dragonflies. Luckily the weather was cloudy and misty a lot of the time, so I could reasonably well concentrate on the birds (great birds!), but nevertheless almost every day unexpected spring findings occurred. Over the next days there is a lot to research, I am afraid. I know that Vietnam is not very well researched, but this is ridiculous! And I need help, so if you have suggestions to the species in the photos, tell me! Otherwise, more will become clear, hopefully, in the next days.

Let's start in Xuan Son (April 12 and 13)
Over the two cloudy days we encountered 27 species. Big surprise was Archineura hetaerinoides, with at least 2 females and 4 males present. Mnais mneme was very common on little streams, with dozens of males and females around. On the same heavily vegetated small streams under forest cover (but also some mixed with abundant Euphaea masoni on the bigger streams) Euphaea guerini, another species I had not seen before. Protosticta grandis was another addition to the Xuan Son list. I encountered about 6. Both Coeliccia poungyi and C. sasamotoi were already around, the former with one individual, but the latter common. Best species, maybe, was a damsel not uncommon along the forest track close to the first stone bridge. I have as yet no idea what it was, but it was beautiful. I saw only males, 2 on the 12th and 4 on the 13th, perched on top of leaves close to the forest floor or up in bushes. And there was a common Gomphid of which I saw many males and a few females, a species of Nihonogomphus I identified as N. schorri, known only from Huu Lien. Last but not least, on both days I saw Philoganga vetusta, a male and a female.

Let's start with the unknown. Any ideas?

Archineura hetaerinoides, male

Ochre Titan revisited, Philoganga vetusta, female

Protosticta "grandis", immature male

Nihonogomphus schorri, great range extension

And Coeliccia poungyi, a crisp male

Tam Dao! Ochre Titan!*

*Adjusted after true identity of C. mortoni was established as C. haksik and again after it became clear that C. mingxiensis is just a synonym of C. cyanomelas (removed from this entry).

Today, April 9, I went to Tam Dao with my birding pal Hein. The birding was okay, but it was rather misty, so it could have been better. Halfway the afternoon it became better and we even had a little weak sun, so we went to the Belvedere Resort surroundings and ran into several very cool damselfly species along the trail. 3 of these I had not seen before. And two of these belonged to genera I had not seen before in Vietnam and one even to a family that was new to me! The adrenalin!

The prize of the day goes to the fresh male of the magnificently weird Philoganga vetusta, as large as it is weird really. A frightening damselfly, measuring 7.5 solid heavy-bodied centimeters. The other new species was Rhipidolestes owadai, of which I saw both male and female Coeliccia scutellum created some confusion, as the fresh males looked rather different from what I am used to. Finally, the fourth species was a fresh female Calicnemia mortoni.

This is exactly as Hein (thank you!) spotted it perched, immature male Philoganga vetusta

In hand. The colors are starting to show, but for the real thing, visit Sebastien's page.

Head in close-up.

And the very simple appendages in ventral view.

Male Rhipidolestes owadai. Note the spine on S9. A wonderful species.

The female is rather similar to the male, but less dark on the wingtips

Immature male Coeliccia scutellum. Much yellower on flanks, prothorax and abdomen.

C. scutellum close-up. See also dorsal pattern of head, almost absent in mature male

Female C. scutellum, likewise immature and with more extensive yellow on S9-10.

And finally, immature female Calicnemia haksik