Stylurus kreyenbergi ( Ris 1928 )

Wilson, Keith Duncan Peter & Xu, Zaifu, 2009, Gomphidae of Guangdong & Hong Kong, China (Odonata: Anisoptera) 2177, Zootaxa 2177, pp. 1-62 : 23-26

Stylurus kreyenbergi ( Ris 1928)

Figs. 11 (a–f)

Gomphus kreyenbergi Ris 1928 : Ris (1928: 273, type-loc. “Jentschoufu, Schantung”, Shandong); Needham (1930: 54– 55, “Shantung”, Shandong); Schmidt (1931: 186–187, figs 9, “Ling-Pin-Bezirk”, Zhejiang); Navás (1936: 38, “Kuling”, Jiangxi).

Burmagomphus kreyenbergi Ris 1928 : Chao (1954: 80, Jiangxi, Shandong & Zhejiang); Chao (1983: 100, Jiangxi, Shangdong & Zhejiang); Davies and Tobin (1985: 25, China); Steinmann (1997: 98, China).

Gomphus sp. ( annulatus Djakonov ?) nec Djakonov 1926: Asahina (1961a: 3, figs 23–26, “Lien-hwa-tung”, Lushan, Jiangxi).

Stylurus kreyenbergi Ris 1928 : Chao (1990: 131–133, 10 figs, Jiangxi, Shandong, Zhejiang); Bridges (1994: VII.127, VIII.66; Tsuda (2000: 114, China); Hua (2000: 12, Jiangxi, Shandong, Sichuan, Zhejiang).

Specimens: 1 ♂ Panyu, Guangzhou, 9 viii 2002, coll. KW.

Description: Small to medium-sized, yellowish Stylurus with markedly hooked posterior hamulus and transverse ridge above lateral ocelli. Labrum predominantly yellow with distal margin black, anteclypeus black, postclypeus black with yellow spots laterally and yellow triangular spot at distal, central margin ( Fig. 11a). Dorsum of frons with transverse yellow crest. Pair of prominent, linked, transverse, apically rounded ridges above lateral ocelli. Yellow occiput with lateral and basal margins finely black. Large yellow spot at rear of head, behind and below occipital margin. Synthorax black with short yellow, isolated dorsal stripes and long, yellow antehumeral stripes ( Figs. 11b–c). Sides of synthorax black with broad yellow stripes across the mesepimeron, metepisternum and metepimeron. Yellow stripes across mesepimeron and metepisternum broadly conjoined centrally. Dorsum of abdomen mainly black; S1 and S2 with central yellow spots and sides yellow ventrally, S3–6 with narrow yellow basal rings, S7 with small, semi-circular yellow spot at base and ventero-lateral yellow spots, S8 and S9 each with large yellow spots at base of dorsum and large venterolateral yellow spots, S10 yellowish at sides and blackish-yellow above ( Fig. 11d). S7–9 broadly expanded. S6–10 yellow ventrally (bright yellow S7–9). Posterior hamulus parallel sided and roundly hooked with a well defined shoulder at the base of the hook, angled at ca 90º to shaft ( Fig. 11f). Superior appendages short, noticeably bent inwards at middle, with prominent lateral tooth at outer margin, located just beyond centre ( Figs. 11d–e).

Measurements (mm): Japanese specimens: abd. + app. 42–44, hw 33–35 mm; China ♂: abd. + app. 40.0–42.0, hw 30–34 mm.

Remarks: Asahina (1961a) commented on specimens obtained from Jiangxi: “This species will be identical with Gomphus kreyenbergi Ris described from Shantung, and also with the Ussurian Davidius annulatus Djakonov. A detailed taxonomic discussion will be made in a future occasion.” To our knowledge Asahina never published any further comments or discussion on the synonymy of these two taxa. The two taxa have similar colour patterns and similar structure of caudal and secondary genitalia. Both possess a roundly hooked, sharply pointed posterior hamulus which is erect with parallel sides. The yellow stripes across the mesepimeron and metepisternum are not broadly conjoined centrally in Japanese specimens (see Sugimura et al. 2001). The distribution of Stylurus annularis ( Djakonov 1926) includes China (Heliongjiang), Korea, Japan (Kansai Region, Central Honshu) and Russia (Southern Far East-Ussuri).

The male specimen captured at Panyu on 9 August 2002 was one of several freshly emerged individuals observed at the riverside in the industrial setting of urban Guangzhou. The teneral dragonflies were found on the banks of a deep, broad, muddy leat of the Pearl River delta. The larvae can clearly tolerate moderate to high levels of organic pollution in an urban enviroment setting. This species is recorded from Guangdong for the first time and represents the most southern and western record of this species.

Distribution: China (Guangdong, Jiangxi, Shandong, Sichuan? & Zhejiang).