(Figures 9–12)
Holotype. 1 ♂, Doi Cao, Bao Loc District, Lam Dong Province (11.64306 N, 107.6889 E, altitude 746 m), 15.iv.2017, Quoc Toan Phan leg.
Paratypes. 1 ♀, same data as holotype; 4 ♂♂, 2 ♀♀, same location, 12.xii.2016, Dang Ngoc Van leg.; 1 ♂, Dong Tien Commune (11.29833 N, 107.9906 E, altitude 776 m), Ham Thuan Bac District, Binh Thuan Prov., 1.x.2015, Dang Ngoc Van leg.; 1 ♂, Hoa Phong Commune (12.47806° N, 108.4617° E, altitude 749 m), K’Rong Bong District, Dak Lak Prov., 10.iv.2017, Dang Ngoc Van leg.
Type deposition. All type specimens of the new species are deposited in the ZCDTU, Danang city, Vietnam.
Etymology. Wildermuthi, a noun in the genitive case, after Hansruedi Wildermuth (born in 1941) from Switzerland, in appreciation of his support of the first author’s odonatological research in Vietnam via the International Dragonfly Fund.
Description of holotype. Head (Fig. 10a). Labrum pale yellow, black along free margin. Genae and anteclypeus pale yellow. Mandible bases dark reddish. Postclypeus, vertex, frons, occiput and underside of head black entirely black. Ocelli yellowish. Antenna dark yellowish, basal segment black.
Thorax (Fig. 10a–c). Prothorax. Propleuron almost entirely dark brown and black. Anterior pronotal lobe dark yellowish; middle pronotal lobe mostly dark. Posterior pronotal lobe black, free margin rounded in lateral view (Fig. 10b). Synthorax (Fig. 10a). Mesepisternum, mesepimeron entirely black. Metepisternum black with a yellowish stripe, covering the spiracle and connected to metakatepisternum, not reaching the wing bases. Metepimeron entirely yellow. Legs (Fig. 10a). Coxa and trochanter entirely yellow; femur yellow, darker distally; tibia pale brown with narrow, faint, irregular dark stripe along much of extensor surface; tarsus and claw dark yellow. Wings. 14–15 Px in both wings. Pterostigma (Fig. 11c) dark brown centrally, irregularly yellowish around this, covering slightly more than one underlying cell.
Abdomen (Figs 9a, 11a–b). S1–2 dark brown above, yellowish below. S3–8 dark brown, black apically with broad pale basal annulus, poorly delineated pale areas laterally, these large on S3–4, becoming smaller on successive segments except S8 where there is a large yellowish area laterally. S9 blue dorsally, dark brown and black below, dark yellow at margin of tergite, sternite dark yellow. S10 black with a blue mark dorsally, ventrally dark yellow (Fig. 11a–b).
Anal appendages (Fig. 12a–c). Cerci dark brown and paraprocts yellowish with brown areas dorsally and apically, both are ca. 3 times length of S10. In lateral view cerci strongly arched, broad at base, narrower at middle point and then downturned and gradually expanding to rounded apices; in dorsal view narrowing from base and expanding slightly at apices where somewhat hollowed interiorly, converging strongly at apices, which overlap. Paraprocts broad at base and narrower to the tip, simple structurally without subbasal spurs, in dorsal view converging at apices, in lateral view directed slightly upward so that apices are obscured by the cerci. Genital ligula (Fig. 12d) of typical form for the genus with two short flagella that are slightly expanded distally so approximately spoonshaped.
Measurements (in mm). Abdomen with anal appendages 35, Hindwings 24.
Description of female paratype. As male except as noted: middle pronotal lobe of prothorax largely brownish; latero-distal margin of posterior pronotal lobe with short triangular-shaped processes at the corners of the free margin (Fig. 10d–f). Px 16 in both wings. S7–10 including appendages brownish; ovipositor dirty yellowish, extending beyond cerci (Fig. 11d).
Measurements (in mm). Abdomen with anal appendages 32, Hindwings 24.
Variation in paratype males. In two paratype males from Bao Loc the pale markings on the terminal segments of the abdomen are yellow, not blue as in the holotype. This difference might be due to imperfect preservation by the collector. Px: 14–16 Px in both wings; Measurement (in mm): Abdomen with anal appendages 35–38; Hindwings 23–25.
Variation in paratype female. Body color pattern, Px count and the measurements of the paratype female not different from the paratype used for the description of the female.
Differential diagnosis. The male of D. wildermuthi sp. nov. is easily distinguished from all other species in the D. carmichaeli -group except D. tenella by the form of its anal appendages, with the cerci seen in lateral view (Fig. 12b) only gradually expanding from the downturn to rounded apices. It is distinguished from D. tenella by having S8 without pale coloration dorsally but such coloration present on S9–10 (Fig. 11a–b), the opposite condition is seen in D. tenella.
Remarks. Judging from the illustrations in Lieftinck (1935) D. wildermuthi sp. nov. is also distinguished from D. tenella by the lack of subbasal spurs on the paraprocts, this character is not mentioned in the diagnosis above only because insufficient material of D. tenella has been checked to be sure that the subbasal spurs are always present.
Distribution. Vietnam (Dak Lak, Lam Dong & Binh Thuan Provinces) (Fig. 13).