Chlorogomphus gracilis Wilson & Reels, 2001

Figs 47–60, 63

Material examined

VIETNAM – Kon Tum Province • 2 ♂♂; Dak Glei District, Ngoc Linh Commune, Ngoc Linh Nature Reserve; 15.0444° N, 107.9270° E; alt. 1480 m; 5 Jun. 2019; Q.T. Phan leg.; ZCDTU 2019060501-ODO to 0502-ODO • 1 ♀; same collection data as for preceding; ZCDTU 2019060503-ODO • 1 ♂; same locality as for preceding; 12 May 2017; Dang Ngoc Van leg.; KPMNH 2017051201.

Remarks

Chlorogomphus gracilis is a new record for the Vietnamese fauna and for continental Asia. The body coloration and all structural features of the Vietnamese specimens (Figs 47–60) agree well with the original description of C. gracilis from Hainan. There is only one exception, i.e., that the epiproct of the Vietnamese specimens is gently expanded apically (Fig. 58), whereas in the Chinese C. gracilis it is narrower from its base to the tip (Wilson & Reels 2001: fig. 77; Zhang 2019: 530). Wilson & Reels (2001) considered C. gracilis as similar to C. fraseri by the similarity of having a peg-like process in the epiproct, but the illustrated epiproct from the holotype has only a single process arising from the center. Wilson & Reels (2001) described the “hooked peg-like process arising from the centre of the base plate formed by the two conjoined inferior appendages”. This process on the epiproct of the holotype of C. gracilis (Wilson & Reels 2001: fig. 77) differs from conditions in the Vietnamese specimens, which have two long erect spines rising from the base of the epiproct (Figs 58–59) that are not conjoined. Zhang (2019: 530) also provided two photos of the anal appendages of C. gracilis from Hainan, but the structure of the process arising from the basal epiproct is not clearly visible in lateral and dorsal views. We consider that the single peg-like process, albeit formed from conjoined pegs, described and figured in Wilson & Reels (2001: fig. 78) is an eXtraordinary character within the genus (with several other species of Chlorogomphus having two separate spines arising from the base of the epiproct; see, e.g., Fig. 13 for C. hoaian sp. nov. and Fig. 16 for C. fraseri). We cannot verify differences in other characters such as secondary genitalia and the vesica spermalis between specimens of C. gracilis from Vietnam and Hainan, since Wilson & Reels (2001) did not provide sufficiently detailed drawings of these structures in their original description. Keith Wilson kindly supplied us with detailed images of the head and the abdominal tip of female C. gracilis from Hainan. The shape of the vertex and valvula valvae of the Hainan specimen appear to be identical to conditions in our Vietnamese female (Figs 51, 57).

Habitat and ecology

Chlorogomphus gracilis was observed only at a small rocky stream on a high mountain (altitude nearly 1500 m) near a main road. We conducted surveys at other streams at elevations of 1000–2000 m along the same road but did not find any other individuals of this species or any other Chlorogomphidae.

Distribution

Vietnam: Kon Tum (Ngoc Linh Nature Reserve) Province; China: Hainan Island (Fig. 63: red triangle).