Asiagomphus auricolor ( Fraser, 1926 )

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), Zootaxa 4462 (3), pp. 301-330 : 303-308

publication ID	https://doi.org/ 10.11646/zootaxa.4462.3.1
publication LSID	lsid:zoobank.org:pub:75D121A7-F718-4F69-9E33-E82AB371403A
DOI	https://doi.org/10.5281/zenodo.5974765
persistent identifier	https://treatment.plazi.org/id/03C887DB-6067-8C06-FF67-D52B1BA8FDBE
treatment provided by	Plazi
scientific name	Asiagomphus auricolor ( Fraser, 1926 )
status

Treatment

Asiagomphus auricolor ( Fraser, 1926) View in CoL

( Figs. 4a–b View FIGURE 4 , 5d View FIGURE 5 , 6d View FIGURE 6 , 7d View FIGURE 7 , 8a View FIGURE 8 , 9e View FIGURE 9 , 10a–c, e–f View FIGURE 10 )

Asiagomphus auricolor: Fraser (1926) View in CoL pp. 482–483, fig. 4a [description of female]; Ellenrieder et al. (2015), p. 5 [species list].

Material examined: 1 ♂, Huu Lien NR, Lang Son Prov., northern Vietnam, 1-V-2014, TK leg. ; 1 ♂, same location and collector, 24-V-2014 ; 2 ♂♂ 1 ♀ [used for description], Bac Kan Prov., northern Vietnam, 26-VI-2014, TK leg. ; 1 ♂ [used for description], Huu Lien NR, Lang Son Prov., northern Vietnam, 19-IV-2015, TK leg. ; 1 ♂, Pia Oac NR, Cao Bang Prov., northern Vietnam, 17-VI-2015, TK leg. ; 1 ♂, Ha Tay, Ba Vi NP, Ha Noi, northern Vietnam, 29-VI-2015, TK leg.

Additional records based on field observations by TK: 1 ♂, Huu Lien NR, Lang Son Prov., northern Vietnam, 21-IV-2014 ; 5 ind., same location, 26-IV-2014 ; 14 ind., same location, 1-V-2014 ; 10 ind., same location, 24-V-2014 ; 1 ind., Bac Kan Prov., northern Vietnam, 21-VI-2014 ; 1 ind., same location, 22-VI-2014 ; 1 ♂, same location, 24-VI-2014 ; 1 ♂, same location, 25-VI-2014 ; 3 ♂♂, Pia Oac NR, Cao Bang Prov., northern Vietnam, 25- VI-2014 ; 3 ♂♂, Bac Kan Prov., northern Vietnam, 26-VI-2014 ; 8 ind., Lang Son Prov., northern Vietnam, 28-VI- 2014 ; 1 ♂, Cao Bang Prov., northern Vietnam, 29-VI-2014 ; 2 ind., Bac Kan Prov., northern Vietnam, 6-VII-2014 ; 5 ind., Huu Lien NR, Lang Son Prov., northern Vietnam, 22-III-2015 ; 5 ind., same location, 19-IV-2015 ; 7 ind., Cao Bang Prov., northern Vietnam, 30-IV-2015 ; 2 ind., same location, 23-V-2015 ; 15 ind., Thai Nguyen Prov., northern Vietnam, 15-VI-2015 ; 1 ♂, Cuc Phuong NP, Ninh Binh Prov., northern Vietnam, 16-VI-2015 ; 2 ind., Huu Lien NR, Lang Son Prov., 19-III-2016 ; 1 ♂, Cuc Phuong NP, Ninh Binh Prov., northern Vietnam, 16-IV-2017 ; 1 ind., Cuc Phuong NP, Ninh Binh Prov., northern Vietnam, 11-VI-2017 ; 1 ♂, Bac Kan Prov., northern Vietnam, 8-VII-2017 .

First description of male ( Figs. 4a–b View FIGURE 4 , 5d View FIGURE 5 , 6d View FIGURE 6 , 7d View FIGURE 7 , 8a View FIGURE 8 ). Head. Labium, labrum, postclypeus and antefrons black. Anteclypeus dark brown. Base of mandibles pale yellow. Postfrons with broad yellow stripe, extending anteriorly just down the antefrons, and posterior edge of postfrons black. Cranium black, lateral ocelli framed with a raised ridge posteriorly. Occiput dark brown, wrinkled and slightly raised centrally, occipital ridge with long black hairs. Antennae black, but top of first segment pale.

Thorax. Prothorax black, but anterior lobe with central yellow spot, and median lobe with small yellow central spot and pair of lateral spots. Synthorax black with pale yellow markings as follows: Mesepisternum with dorsal stripe, widening anteriorly and confluent with collar stripe to form two inverted “7” shapes. Small antehumeral spot towards dorsal end of humeral suture. Mesepimeron almost completely covered by broad lateral stripe. Mesokatepisternum blackish brown with large yellow spot. Metepisternum with broad lateral stripe, somewhat constricted just below dorsal end and bordered by clear black stripe over interpleural suture, running through spiracle, margins of yellow stripe less distinct ventrally. Metakatepisternum brown with diffuse yellow center. Metepimeron almost completely yellow, but black stripe over metapleural suture. Coxae and legs all black.

Abdomen. Black with yellow markings as follows: S1 yellow with small black area dorso-laterally covered in long black hairs; S2 yellow with black marking dorsally of yellow auricle, continuing posteriorly over dorsum, but interrupted in middle over dorsal central line by yellow stripe; S3 with antero-ventral spot and short narrow anterodorsal stripe; S4–7 with antero-dorsal half-ring, interrupted dorsally by thin black line on S7; posterior half of S9 with large dorsal mark. S7–9 markedly widened.

Accessory genitalia ( Figs. 4a–b View FIGURE 4 ). Black, anterior hamulus about 4x longer than wide, apical third constricted, minimally curved inwards and posteriorly at apex, latero-posterior margin of constricted part with distinct small teeth. Posterior hamulus robust, in lateral view 3x length of visible part of anterior hamulus, lateral surface deeply concave in middle part, apex directed inward and anteriorly to form robust hook, lateral surface smooth, without ridge crossing surface distal of concave part and anterior margin smooth in lateral view.

Vesica spermalis . Flagellum extending well beyond median process of apical segment.

Wings. Hyaline with black veins, minimally tinted amber at base. Anal triangle 3-celled, cubito-anal space with one crossvein, all triangles uncrossed, nodal index 12–19:18– 14 in FW, 15–12: 14–15 in HW. Pt brown, 4 mm, covering 5–6 cells in FW and 6–7 in HW.

Anal appendages ( Figs. 5d View FIGURE 5 , 6d View FIGURE 6 , 7d View FIGURE 7 , 8a View FIGURE 8 ). Black. Cerci simple, unbranched, widely diverging in dorsal view and apically tapering to a posteriorly directed point ( Fig. 5d View FIGURE 5 ), in lateral view minimally curved downward at mid-point, apically inflicted upward to form up-slanting spike, in length cerci approximately 1.5x length of S10 ( Fig. 6d View FIGURE 6 ). Epiproct deeply bifid, in dorsal view branches rounded, simple ( Fig. 8a View FIGURE 8 ), diverging in same measure as cerci ( Fig. 7d View FIGURE 7 ). In lateral view relatively straight, upper margin slightly concave, lower margin somewhat rounded, its lowest point one-third from base, its apical two-thirds becoming thinner towards apex. Slightly longer than cerci, apex a blunt point, hooked inward and upward to form small dorsal tooth ( Fig. 6d View FIGURE 6 ). Posterior margin of epiproct between branches straight, separation between branches about 1.3x wider than length of protruding part of branches ( Fig. 7d View FIGURE 7 ).

Variation in males. Two of seven specimens without antehumeral spot and with second yellow lateral stripe over metepisternum reduced to postero-dorsal corner. In two more specimens black stripe over interpleural suture broader, including all of spiracle ( Fig. 10b View FIGURE 10 ). Yellow spot on mesokatepisternum somewhat variable in size, metakatepisternum varying from all yellowish brown to all dark brown. In one specimen black on S2 reduced, in another more extensive, forming complete dorso-lateral stripe ( Fig. 10c View FIGURE 10 ), and in one male black connecting across dorsum along posterior margin. Yellow marking on S9 varying between only posterior one-third to three-fifths of segment. In two specimens tiny lateral yellow mark at posterior margin of S8 ( Fig. 10b View FIGURE 10 ). In one male yellow halfring on S4–7 reduced to dorsal spot. In one male cerci as long as epiproct in lateral view. In one specimen a second crossvein in cubito-anal space in one FW and one HW. 12–18 Px in FW, 16–21 Ax in FW, 12–17 Px in HW and 11–14 Ax in HW.

Measurements (in mm). Total length (incl. appendages) 60–63, HW 38–41.

Redescription of female ( Figs. 9e View FIGURE 9 , 10e View FIGURE 10 ). As holotype male, but raised ridges posterior to lateral ocelli with spike at posterior end, and occipital ridge with central spike ( Fig. 9e View FIGURE 9 ). Antehumeral spot reduced on one side ( Fig. 10e View FIGURE 10 ) and absent on other side. Second yellow lateral stripe as wide as black stripe over interpleural suture. S2 completely yellow apart from black postero-dorsal marking covering about one-fourth of dorsum of segment. S3 with only small anterolateral spot and no dorsal spot. S8 with minimal yellow line along anterior margin. S9 with postero-dorsal mark covering about two-fifths of segment. Cerci conical, black, as long as S10. Nodal index 15– 18:19–16/17–12:13–16.

Variation in females. Based on a photo of a female caught on 26-IV-2014 ( Fig. 10f View FIGURE 10 ), S1–2 with broad dorsolateral black line completely bisecting the yellow marking. Thorax with distinct antehumeral spot. Cerci whitish. This is a much fresher individual.

Measurements (in mm). Total length (incl. appendages) 63, HW 41.

Discussion. When Fraser described Gomphus auricolor , he knew only few similar species (notably Gomphus (= Asiagomphus ) nilgiricus (Laidlaw, 1922)) and therefore judged the extensively yellow S1–2 of his female to be sufficient to separate his species novum from all others. “The species belongs to the group nilgiricus by its parallel antehumeral [sic] stripes broadly confluent with the short mesothoracic collar, but is easily distinguished from that and all others of the genus [ Gomphus , TK], by the strikingly broad expanse of bright yellow at base of abdomen, a feature which at once meets the eye.” ( Fraser 1926, p. 483). Although the pattern of S1–2 of most Asiagomphus species contains large yellow areas, they almost invariably have longitudinal dorso-lateral black stripes on S2. This is also true for all species from northern Vietnam, from where A. auricolor was described, apart from A. acco , which has identical S1–2 to Fraser’s description, but which has completely black metepisternum and paired postero-dorsal abdominal spots instead of complete half-rings. As is obvious from the female in Fig. 10f View FIGURE 10 , which has a large dorso-lateral black stripe on S1–2 exactly like the male in Fig. 10c View FIGURE 10 , even in A. auricolor almost completely yellow S1–2 is not a consistent character. However, females with almost completely yellow S1–2 are not infrequent. The specimen used for description here is one such specimen. It otherwise also fits the description provided by Fraser, apart from the color of the cerci, which appears to be variable (see Fig. 10f View FIGURE 10 ). It also on one side has a vestigial antehumeral spot, another variable character, as is clear from the variation in males, in some of which the antehumeral spot is absent and in others present. In the male specimens studied the lack of antehumeral spots occurs in combination with reduced second yellow lateral stripe and darkened and worn wings. The same is true of the female used for description, so it appears likely that the antehumeral spot often becomes obscured in older specimens.

There are no other Asiagomphus species in northern Vietnam that so closely fit the original description by Fraser and have almost completely yellow S1–2. The described female was caught in close association with several males of a species of Asiagomphus that occurs widely in northern Vietnam, but does not fit the description of any other known species. These males too have extensively yellow S1–2 and most often a yellow stripe over the metepisternum. These are here described as the male of A. auricolor and its differential diagnosis is provided.

Differential diagnosis. The male of Asiagomphus auricolor must be compared with all known Asiagomphus species, to ascertain it is not a junior or senior synonym of currently known species. Most Chinese, Korean, and Japanese species can easily be eliminated on the basis of combinations of patterning and structural characters. Notably, most of these species have a distinct complete antehumeral stripe in addition to the dorsal stripe, and have lengthwise dorsal stripes on the abdomen. Chao (1990) separates A. motouensis Liu & Chao, 1990 from all other species in his key as the only species that combines a black occiput with an antehumeral spot, but lacks an antehumeral stripe. However, A. motouensis has a completely different thorax pattern, lacking a continuous black stripe over the intrapleural suture and more slender dorsal stripes. The Japanese endemic species all have a complete antehumeral stripe and three out of four have a longitudinal pattern on the abdomen. The fourth, A. yayeyamensis (Matsumura in Oguma, 1926) , has triangular dorsal spots on the abdomen, lacks a black stripe over the interpleural suture, and its female has extensively black S1–2. Asiagomphus acco has black abdomen, black metepisternum, and different cerci. Asiagomphus reinhardti is easily identified by its protrusion of the posterior margin of S10 and different cerci. Asiagomphus giza Wilson, 2005 is only known from a female, but has a peculiar triple horn on the occiput, lacking in the female used for description, and has longitudinal markings on the abdomen. The western species A. nilgiricus ( Laidlaw, 1922) and A. personatus (Selys, 1873) , whether or not synonyms ( Fraser 1934), have longitudinal markings on the abdomen ( Fraser 1925) and A. odoneli (Fraser, 1922) has differently marked S9, without postero-dorsal yellow spot, but with lateral markings instead. Asiagomphus xanthenatus ( Williamson, 1907) is closer in appearance to A. auricolor , with half-rings at the base of abdomen segments, but its epiproct has widely diverging branches separated by its semicircular posterior margin ( Fig. 5e View FIGURE 5 ), and the apical hook of the posterior hamulus is directed more anteriorly, not inwardly, whereas the anterior margin of the posterior hamulus is clearly angular with small teeth, not smooth ( Fig. 3e View FIGURE 3 ). Asiagomphus coreanus (Doi & Okumura, 1937) , endemic for the Korean Peninsula, has complete antehumeral stripe and interrupted black stripe over interpleural suture, and different appendages, whereas A. melanopsoides from Korea and the Russian Far East also has complete antehumeral stripe and longitudinal stripe over the dorsum of the abdomen. Asiagomphus gongshanensis was described from a female specimen, and is said to resemble A. personatus . The poorly known A. corniger (Morton, 1928) has completely different anal appendages. Indeed, Chao (1990) chose to include it in Burmagomphus Williamson, 1907 . Asiagomphus somnolens (only known from a female) has all yellow labrum.

From the above it is clear that the taxon here described as the male of Asiagomphus auricolor is different from all known Asiagomphus species with known males, and differs in color pattern from the species known only from females as well. It is also easily separated from the three new species described in this paper. Asiagomphus monticola and A. superciliaris are much darker and have different posterior and anterior hamuli, and differently shaped epiproct. Asiagomphus kosterini has completely different abdomen pattern and different anal and secondary appendages. The identification of the female is a challenge. It is not clear how consistent the combination of horns on the cranium and occiput of female Asiagomphus species is, but my experience with for instance A. reinhardti (see also under that species) indicates it may well vary considerably between females of the same species. More specimens must be studied to establish the range of variability. However, from my personal observations it appears that also female specimens only tentatively identified as A. auricolor (some specimens could not be conclusively identified, because of differences with the original description by Fraser and the fact they were not caught in copula with the type of male described here as male A. auricolor ) sometimes lack a central spike on the occiput and may have additional spikes adjacent to the lateral ocelli. Cerci may be pale or black ( Figs. 10e–f View FIGURE 10 ). Antehumeral spot may be present or absent (as in the male). Currently, only females with almost completely yellow S1–2, dorsal halfrings on abdomen segments and at least some pale markings on the metepisternum can be positively identified as A. auricolor . The female in Fig. 10f View FIGURE 10 was also caught in close association with typical males of A. auricolor .

I am confident that the combination of females from northern Vietnam that closely fit the original description of Asiagomphus auricolor from Tonkin (present day northern Vietnam) and the common occurrence of males that are clearly different from all currently known species and can be considered topotypical with A. auricolor provide a good enough case to consider this taxon as the elusive A. auricolor , rather than describing it as a new species, which would be the only alternative.

Habitat and ecology. Asiagomphus auricolor is a rather common species found at a variety of smaller streams in semi-open areas, where they generally perch on vegetation by the side of the streams. It is a difficult species to approach and quickly alights when disturbed, flying up into tree cover. They start emerging from the middle of March as one of the earliest species in northern Vietnam, together with for instance Trigomphus kompieri Karube, 2015 . By the beginning of July only few survive.

Reels & Zhang (2015, pp. 276–277) illustrate a similar looking species from Hainan as Asiagomphus sp., although it has larger lateral markings at the posterior margin of S8 and yellow spots on the labrum. The description mentions (p. 277) that “Males perch on the surface of leaves, close to the stream. Very easily disturbed.” It will be interesting to compare these taxa.