Burmagomphus dentatus Zhang, Kosterin & Cai, 2015, sp. nov.

Burmagomphus dentatus sp. nov.

Figures 19–26, 37

Burmagomphus sp.— Zhang 2011 (Zhangjiang River, Libo County, Guizhou Province, China)

Etymology. dentatus is a Latin adjective meaning ‘with teeth’; this epithet was applied because of characteristic teeth on the cerci.

Material examined. Holotype: ♂, Zhangjiang River in Xiaoqikong scenic spot (25°15’06’’N, 107°44’37’’E), altitude 410 m, Libo County, Guizhou Province, China, 0 8 July 2010, Hao-miao Zhang leg.; Paratypes: 1♂, same data as holotype male; 1♂, 2♀, same site and collector, 0 7 June 2010.

Holotype male: Head. Eyes green while alive (Fig. 37). Face black with pale yellow markings (Fig. 19). Labium largely pale yellow, anterior margin of middle lobe black. Mandible bases pale yellow. Labrum with a pair of very large oval pale spots. Anteclypeus entirely black, lower margin of postclypeus with a central yellow stripe. Top of frons with a very broad yellow stripe. Vertex black with paired crescent tubercles behind lateral ocelli. Occiput black, with hind margin straight, fringed with long setae.

Thorax. Generally black with pale yellow markings (Fig. 20). Prothorax with a pale spot on each side of middle lobe. Synthorax with mesothoracic collar interrupted at mid point, dorsal stripes not connecting with collar stripes. Antehumeral stripe extends throughout mesepisternum length but finely interrupted at its lower end. Sides of synthorax largely pale yellow with two broad black stripes, one along interpleural suture, the other along metapleural suture, thus forming three broad yellow stripes. Mesokatepisternum and metakatepisternum with large yellow spots. Legs largely black. Coxae with yellow spots in all legs, fore leg femur with inner yellow stripes.

Wings. Hyaline, venation black. Forewings: 13 antenodals above and below Sc; 11 (left) and 9 (right) postnodals above R1, 11 (left) and 12 (right) postnodals below R1. Hindwings: 10 (left) and 9 (right) antenodals above Sc, 8 (left) and 10 (right) antenodals below Sc; 9 postnodals above R1, 12 below R1. Triangles not crossed. Median space without crossvein. Anal loop one-celled. Anal triangle 3-celled. Pterostigma brown, well braced, below covering 3 (left) and 4 (right) cells on forewings, 4 cells on hindwings.

Abdomen. Black with pale marking as follows (Fig. 37): S1 with a large spot laterally and a dorsal spot connecting with dorsal spot in basal half of S2; sides of S2 with two oval pale spots, proximal one including auricles; S3–7 with a basal ring; S9 with a very large dorsal spot posteriorly; S10 and anal appendages black, without a spine. Cerci slightly longer than epiproct and S10, tapering and finely pointed, with a tuft of setae at apex, converging in dorsal view (Fig. 21). In lateral view, cercus slightly curved, its lower margin with a large blunt median tooth directed downwards; cercus apex kinked up and very narrow (Fig. 22). Epiproct with a deep median concavity, thus forming two relatively long lateral diverging branches, in lateral view their tips slightly curved upwards (Figs. 21–22). Posterior hamulus rather narrow at base and very strongly broadening apically, with posterior and apical sides nearly straight, forming a prominent, acute but rounded angle, and a convex anterior side; postero-apical spine very broad, tooth-like (Fig. 23).

Female: Head and thorax color pattern similar to male (Figs. 24–25), vertex with two parallel horns behind and centrally of lateral ocelli (Fig. 24). Wing bases slightly tinted with amber. Abdomen with a big yellow spot on either side of S1 and S2. S1 with a dorsal spot connecting with dorsal spot in basal 2/3 of S2; S3–7 with a basal ring; S3 also with an additional small lateral spot; S9 and S10 with dorsal spots posteriorly. Vulvar lamina shown in Fig. 26

Variation in paratypes. In one paratype male the middle lobe of labium is largely black with a small yellow spot, and the size of paired spots on labrum varies.

Measurements (mm). Holotype male: total length 49.0, abdomen (including anal appendages) 37.0, hind wing 28.5; Paratype: males: total length 52.0–53.0, abdomen (including anal appendages) 38.0–40.0, hind wing 29.5–30.0; females: total length 51.0–52.0, abdomen (including anal appendages) 39.0–40.0, hind wing 31.0–33.0.

Differential diagnosis. This species also belongs to the conventional group 3 with two parallel light stripes on the mesepisternum. The two complete lateral black stripes along the thoracic sutures make it similar to B. arvalis, B. intinctus (Needham 1930; Chao 1954, 1990), B. apricus, B. magnus (see above) and B. sivalikensis (Fraser 1926, 1934). However, B. dentatus differs well from all species of group 3 but B. sivalikensis in having a strong blunt submedian tooth on the cercus. However, in B. sivalikensis this tooth occupies the lateral position in contrast to B. dentatus, where its position is ventral. Besides, B. sivalikensis has very different male secondary genitalia, with the posterior hamulus narrower and bearing a long pointed process and the vesica spermalis with a peculiar concave posterior margin (Fraser 1926). In B. dentatus, the secondary genitalia exhibit no specific features and are similar to those in most of the group 3 species. In addition, B. dentatus has a black occiput (greenish white in B. sivalikensis) and a less expressed abdominal yellow marking. The ventral cercal tooth in B. intinctus (fig. 7) is scarcely expressed, and the general shape of the appendages is very dissimilar.

Female of B. dentatus is similar to female of B. magnus but has the pair of vertex horns set more closely to each other, so that their bases do not extend as wide as the lateral ocelli, while their apices are upright in parallel. Female of B. intinctus differs well from both above mentioned species by a pair of double short horns behind each lateral ocellus, widely separated by a long transverse vertex ridge (Fig. 9).

Habitat. The type locality, the Zhangjiang River was very wide and deep. The section where the type series was collected was about 30 m wide and about 0.3–0.5 m deep at the banks; the bank vegetation was thick. During fieldwork in the beginning of June 2010, thousands of gomphids were emerging, including B. dentatus, B. gratiosus and B. sowerbyi. No fully mature individuals of these three species were found. During fieldwork in the beginning of July 2010, many mature individuals of both sexes were collected in trees near the river bank; they perched on leaves about 3–5m above ground. All three species were collected at the same tree, B. gratiosus most common, while B. dentatus and B. sowerbyi were rarer.

Distribution. Currently only known from southern Guizhou province, China.