Thursday, 25 June 2015

A Lamelligomphus feast - two additional species

Lamelligomphus is a fascinating genus of pretty much similar looking gomphids with massive and impressive appendages. They have a habit of hovering over fast streams, often again active towards dusk. Absent from Do & Dang, I soon found out that they did in fact occur in northern Vietnam, as is evident from the various entries on the genus in this blog. Additional species occur in the south (for sure L. castor), but I focus on the north. After verifying L. camelus and L. formosanus, both easy to recognize, L. camelus due to distinctive appendages and typical humps on S8 and L. formosanus due to the extensively protruding inferior appendages, raised distal carina of S8 and typical penile organ and thumb-like extension of the anterior hamule, the first hurdle was the unidentified species that recently was described by Karube as L. vietnamensis. This species is very similar outwardly to L. hainanensis, another species often encountered. But L. vietnamensis is larger (similar in size to L. camelus and L. formosanus), without any protrusion of the inferiors, antehumeral stripes connected to collar and line over frons interrupted. Smaller L. hainanensis has similar anterior hamule and penile organ, but generally black labrum (sometimes with two small spots), uninterrupted stripe over frons and normally no connection between antehumerals and collar. Importantly, it has a limited, but obvious, protrusion of the inferior appendages.

So, four species, and all in their inconspicuous ways different. And that was that. Or so I thought. The first crack in this simple scheme occurred on June 13, when I was checking a stream in Nghe An Province. This was a small species, like L. hainanensis. But the pattern of the face and on S2 was different. Triggered by this inspection of the appendages showed the lack of any protrusion. In fact it looked like a miniature L. vietnamensis. Penile organ and hamuli were in accordance with both these species. However, it is neither and appears to be an as yet undescribed species.

On June 22 I had a nightmare of an afternoon in Lang Son, having gotten caught in a terrible thunderstorm on an unpaved road in the mountains that had been turned into something reminiscent of Verdun by trucks. There was no way back and I continued struggling in 4WD motion at a speed of 8km an hour average. Towards dusk I got closer to national road 4 and in flatter terrain and crossing a stream decided to give the last moments of the day a try. The obligatory Lamelligomphus was hovering over the water, but in hand showed many characteristics that I had not seen before. The extensive lateral patterning was one, the indistinct humeral line another. Combined with the lack of a thumb-like extension of the hamulus (verified under the microscope), the lack of raised distal carina and other characteristics L. formosanus could quickly be ruled out. That species, although not in the populations I have seen in Vietnam, does sometimes have more extensive patterning. But it was not that. The key in Chao proved helpful. I tentatively identified it as Lamelligomphus tutulus, an addition to the Vietnamese list, but one that has been verified by Wilson for both Guangxi and Guangdong in neighboring China.

Let's start with something easy: Lamelligomphus camelus, with clear protrusion and humps. It also has a distinct boomerang on S2.
As can be also seen in this specimen in hand. This year alone I have seen this common species in Lang Son, Phu Tho, Bac Giang, Yen Bai, Thanh Hoa, Nghe An and Ha Tinh Provinces.
This is the recently described L. vietnamensis. No protrusion, but fairly large species. No humps and no raised distal carina on S8, amongst others.

Another male in hand. This spring I have seen them in Thanh Hoa, Cao Bang and Lang Son Provinces. Not rare, but not as common as L. camelus.

No this is the exciting L. species novum from Nghe An. No protrusion and only a single egg-shaped spot on S2.

Facial pattern not dissimilar to L. hainanensis, but frons with separation and labrum with spots.

These are its appendages, no protrusion at all.
Compare this to these appendages, of a male L. hainanensis
These are preserved specimens, with L. species novum on top and bottom L. vietnamensis, showing the obvious difference in size.

And no it is time to turn to the star of this blog entry. Lamelligomphus tutulus. Note metepisternum with three separated spots, both a humeral spot and indistinct humeral line, extensive yellow pattern on S1-2.

Facial pattern with large markings on labrum, bases of mandibles and lateral on postclypeus.

Very interesting appendages, protruding well, but different in shape from for instance L. formosanus.

As can also be seen in this dorsal view




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