Saturday, 19 April 2014

Anotogaster sakaii*

*This entry has been modified after I received the article by Karube (2012) on Vietnamese Anotogaster, courtesy of Wen Chi Yeh. After careful consideration of all 5 (!) species recorded and illustrated for Vietnam in the article, I can conclude my specimen is A. sakaii, a species recorded from Tam Dao to Sapa. The only anomaly is that it was recorded around 1000m asl in his specimens. The most important characteristics, apart from the measurements (that are good for A. sakaii, A. gigantica and A. klossi (A. flaveola)) the shape of the appendages excludes A. gigantica, and the completely orange brown mandibles, without yellow base, exclude all but A. sakaii and the somewhat smaller A. chaoi. Measurements of note include the pterostigmata of close to 6mm in both HW and FW and abdomen length of 72mm. Furthermore, the head is very broad, with width of postclypeus : distance lower edge labrum and upper edge antefrons approximately 1.1.

On April 16 I was birding on the slopes of Phan Xi Pang mountain at approximately 2000m asl. We were in a little valley in open terrain, with marshy ground traversed by a few clear small streams. When checking one of the streams I noticed a huge dragonfly that was stuck in the grass, apparently freshly emerged. Its abdomen was bent sideways and it seemed not to be able to fly. In fact it missed the left hindwing.

It was immediately obvious that this was a Goldenring of some sort. Its massive size (97mm, HW 56mm) and the lack of anal triangle in the hindwing pointed me to Anotogaster. It is very similar to Anotogaster sieboldii, but there are some minor differences. Wilson (2005) already pointed out the occurrence of A. sieboldii in Guangxi Province in China and the differences between specimens there and the ones in Japan, but also why he considered them conspecific. My first impression of the appendages was that this also appeared to be A. sieboldii. However, Karube (2012) described 5 species for Vietnam, all also occurring in the Sapa region.

It is clear my specimen belongs to the sakaii-group of Anotogaster, if only based on the orange-brown mandibles, without yellow base. The other species in that group, A. chaoi, has slightly different measurements, notably HW and pterostigmata. It does have a brown antefrons, like my specimen, but I consider this caused by the general stage of the specimen, like other parts of its body that will still darken further.

Anotogaster sakaii, male, as I found it with damaged abdomen
The same insect, showing more obviously the yellow wing bases. 

Although clear yellow on postclypeus, the mandibles are orange-brown, without any yellow on the bases.

Hindwing showing the absence of the anal triangle, hence it is Anotogaster


Dorsal view of the appendages. The bent tips are curved upward and inward, maybe due to pressure from the ground upon which it rested. At the base, best visible in the top cercus in the photo a small but clear tooth.

Clearly visible here are the two ventral teeth (different from the lateral tooth in the previous picture), one pointed ventrally close to the base of the cerci and another at about one third, pointed lateral-ventrally inwards. This feature is shared by several species of Anotogaster, but not all. In A. gigantica, both teeth are obvious in lateral view. In most other species they are only both visible in dorso-lateral view.

View showing the ridges at the apical corners of the lower appendage, which becomes thicker apically.

3 comments:

  1. Have you ever considered this to be A. gigantica!

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  2. Hi Chi Yeh, yes, measurements of the present specimen exceed those given in Fraser (gigantica 49mm), the relatively length of the inferior appendages also does not fit, but of course very little is known about gigantica and no recent records are known. Also, that is a species known only from Myanmar. Its wings are described as hyaline, no mention of yellowish bases.

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  3. According to Karube 2012, A. gigantica was recently recorded from Sapa, Lao Cai prov., N. Vietnam. He gave measurements of his specimens with abdomen length 66.7-69.7mm and hindwing lengthe 53 .4-56.5mm.

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