Asiagomphus xanthenatus
Creators: name: Kompier, Tom
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Gomphidae
Asiagomphus
Asiagomphus xanthenatus

description: Asiagomphus xanthenatus (Williamson, 1907)
(Figs. 3e–f, 5e, 6e, 7e, 10d, 12g)
Asiagomphus sp.: Asahina (1986a), pp. 29–31, figs. 1–6 [females].
Asiagomphus xanthenatus: Asahina (1986b), pp. 9–14, figs. 13–25 [description of Thai specimens]; Yokoi & Souphanthong (2014), p. 37 [scan of male], p. 57 fig. 61 [anal appendages in lateral view], p. 84 [distribution map].
Asiagomphus xanthenatus malayanus: Karube (1990), pp. 21–24, figs. 1–10 [description of dark subspecies and female from Malaysia].
Gomphus personatus: Fraser (1925), p. 658–660 [inclusion of G. xanthenatus as junior synonym].
Gomphus sp.: Asahina (1981), p. 10 [record of female].
Gomphus xanthenatus: Williamson (1907), p. 303, fig. 11 [thorax pattern], pp. 305–308, fig. 33 [anal appendages and secondary genitalia]; Laidlaw (1922), p. 398 [short description].
Material examined: 1 ♂, along road AH17, Quang Nam Prov. (appr. 15.583 N, 107.833 E), 15-V-2016, TK leg.
Additional records based on field observations by TK: 2 ♂♂, along road AH17, Quang Nam Prov. (appr. 15.583 N, 107.833 E), 15-V-2016.
Differential diagnosis. The details of the shape of the secondary genitalia and anal appendages (Figs. 3e–f, 5e, 6e, 7e) in combination with the black metepisternum help to separate this taxon from all other Vietnamese species.
Habitat and ecology. Three males were found in close proximity of each other perched on rocks in a mediumsized open stream, or low on bushes and shrubs by the side of the stream, the stream coming down from a forested valley with heavily logged forest, crossing a main road.
Discussion. Asiagomphus xanthenatus was described as Gomphus xanthenatus by Williamson from Burma (present day Myanmar). Fraser (1925) included G. xanthenatus (= Asiagomphus xanthenatus) in G. personatus Selys, 1973 (= Asiagomphus personatus), because he perceived the differences in thorax pattern to be part of a cline and therefore no basis for separation. Possibly the similarity in structure of appendages of these species, at a time when few representatives of the current genus Asiagomphus and the difficulty to separate them were known, led Fraser to this conclusion. But Williamson had given a detailed description of the abdomen pattern of his G. xanthenatus, which was clearly a ‘ringed’ species, rather than a species characterised by a longitudinal pattern on the abdomen (as is Asiagomphus personatus). Asahina (1981, 1986a) published several female Asiagomphus specimens from Thailand as Asiagomphus sp.. Subsequently he received a male specimen, which he identified as A. xanthenatus. He then published as A. xanthenatus both this male, additional females, and the females formerly only identified as Asiagomphus sp. Although all these specimens were collected from Thailand, they came from a variety of locations, with only the male collected from Thung Yai in Kanchanaburi Province (Asahina 1986b). This raises some doubt whether these specimens all belong to the same species, even if they share similar abdomen pattern. In Vietnam, at least five other species occur with a ringed abdomen. Asahina (1986b) pointed out the differences between A. personatus and A. xanthenatus, supporting the point of view that both are bona species. On the other hand, Asahina did not compare his Thai male to type material of A. xanthenatus, but based himself on the similarity between both the description and the illustrations provided by Williamson (1907). Although his conclusion seems warranted, it remains possible that eventually A. xanthenatus sensu Asahina and A. xanthenatus sensu Williamson turn out to be different. Here, I follow the interpretation by Asahina that his male specimen from Thung Yai is A. xanthenatus.
The Vietnamese male from Quang Nam shares with A. xanthenatus the widely divaricate superior appendages and epiproct branches (Figs. 5e, 7e, 12g), the serrated anterior edge of the posterior hamulus (Fig. 3e), paired yellow spots on the labrum, large yellow basal ring on S3 and basal half-rings on S4–7, large yellow postero-dorsal mark on S9 and small yellow lateral spots at posterior margin of S8 (Fig. 12g). It differs by the absence of an antehumeral spot. Karube (1990) described almost identical specimens from Malaysia as a separate subspecies, A. x. malayanus. His material also lacks antehumeral spots or stripes and has largely black (sometimes completely so) metepisternum. However, labrum and S8 are all black.
Yokoi & Souphanthong (2014) recorded A. xanthenatus widely from Laos, although not as far south as the latitude of Quang Nam. The scan of a male included in their book (p. 37) appears to have a tiny antehumeral spot and small yellow markings on the metepisternum in line with Williamson (1907). It seems reasonable to conclude that the Vietnamese male is well within the range of variability of this rather dark species.
Reels & Zhang (2015, pp. 274–275) illustrate an Asiagomphus species from Hainan as Asiagomphus sp. cf A. xanthenatus. It is very similar in outward appearance to both A. xanthenatus and A. superciliaris. Abdominal markings are particularly close to the individual of A. superciliaris illustrated in Fig. 11d., but the frontal view of the head (p. 275) shows yellow spots on the labrum, absent in A. superciliaris. In view of the otherwise tropical distribution of A. xanthenatus, it is worth investigating the possibility their Asiagomphus sp. cf A. xanthenatus concerns A. superciliaris.
description: Published as part of Kompier, Tom, 2018, The genus Asiagomphus in Vietnam, with descriptions of three new species, and first descriptions of the male of Asiagomphus auricolor (Fraser, 1926) and of the female of Asiagomphus reinhardti Kosterin & Yokoi, 2016 (Odonata: Gomphidae), pp. 301-330 in Zootaxa 4462 (3) on pages 326-327, DOI: 10.11646/zootaxa.4462.3.1, http://zenodo.org/record/1441611