Macrogomphus*

*Somewhat adjusted on December 31, 2019. I left this entry in the blog, because it gives a nice insight in my early involvement with the astounding Odonate fauna of Vietnam, trying to make sense of it all with limited available literature. However, it is not at all in line with current knowledge on Macrogomphus. I left the text as it was, apart from parts in bold and the captions of the photos, adding the proper ID, but please see subsequent entries on Macrogomphus and check Kosterin (2019).  That paper paper addressed the considerable confusion surrounding a group of similar Macrogomphus species, showing, amongst others, that M. guilinensis from Central and northern Vietnam (and China) is a junior synonym of M. albardae, occurring in a variety of distinct forms.

On July 24 we were walking along a slow stream in open area (paddies) in Ba Be National Park when I noticed a large gomphid ovipositing on the muddy bank. I caught it and took some photos before releasing it again. At the time I did not realise it was a Macrogomphus. A week later, on August 2, we were walking in a completely different setting at a very different location, now in the village outside Cuc Phuong National Park, when I spotted a large gomphid sitting on an overhead wire. It was well out of reach, but with a tele lens I was able to take a few shots before it moved off. This again was a Macrogomphus, this time a male.

To my knowledge only two Macrogomphus have been recorded in Vietnam, M. rivularis and M. annulatus. [M. rivularis is in fact a junior synonym of M. albardae] The former species was described in 1914 by Foerster and apparently has not been recorded since. Although I have some pages of the article by Foerster, the relevant pages are missing. In surrounding countries several additional Macrogomphus species have been recorded. Asahina for instance mentions M. borikhanensis, M. thoracicus and M. matsukii [M. borikhanensis is also a junior synonym of M. albardae and M. matsukii is possibly not a valid species] from Thailand. Basically Macrogomphus has two groups, species similar in relation to the dorsum of the thorax. Those with ante-humeral stripes fall into the quadratus group, as do these specimens. The other group has large squares on the dorsum, like M. kerri and M. caudatus.

Of the possible quadratus group species, M. annulatus has the abdominal segments 3-8 all ringed completely, both in male and female. M. borikhanensis has a much darker thoracic pattern, with narrower yellow markings and the caudal appendages for the male are quite different, with the ventral branch very large, extending beyond the upper branches in ventral view. Moreover, the vertex is all black. M. matsukii also has complete rings, both in male and female, different caudal appendages and more extensive light markings on the face.

In fact both specimens are very similar to M. guilinensis [M. guilinensis is yet another junior synonym of M. albardae] as described by Chao (male) and Wilson (female). This species has incomplete rings, a yellow spot on the vertex, small conical caudal appendages with simple valvula vulvae (female), or upper appendages with outer branch longer than interior, and angled inferior appendages (with a "heel"). Also in ventral view, the inferior appendages extent laterally beyond the superior appendages. I am not aware of other records of Macrogomphus guilinensis in Vietnam and with M. rivularis unknown, I welcome comments on the identity of these specimens, but as M. guilinensis occurs in Guangxi, it is likely that it may also occur in North Vietnam.

The female Macrogomphus albardae from Ba Be

The dorsum of the thorax and frons. In fact the seperation in the middle of the yellow stripe on the frons is different from the drawing in Wilson. Tricky.

The ventral side of the tip of the abdomen, showing the vulvar lamina

The dorso-lateral view of the tip of the abdomen, showing the caudal appendages

The male Macrogomphus albardae from Cuc Phuong, high and dry on the wire. The thoracic and abdominal pattern very similar to that of the Ba Be female.

The view from below of wings and caudal appendages, see the close-ups

Close-up of the caudal appendages of the male, showing the inferior appendages protruding laterally beyond the superior appendages and the larger outer branch of the superior appendages

A slightly different angle