Ophiogomphus, Lieftinck, 1964

Ngo, Quoc Phu & Nguyen, Minh Ty, 2021, The genus Ophiogomphus Lieftinck, 1964 in Vietnam, with descriptions of the female of O. minimus Karube, 2014 and O. phantoani sp. nov. (Odonata: Gomphidae), Zootaxa 5061 (1), pp. 134-144 : 141-142

Key to the males and females of Ophiogomphus species of Vietnam

Males

1 Anterior hamulus with anterior branch long and slender occupying about 2/3 of anterior hamuli length ( Fig. 20 ); basal hamulus tooth with a weakly developed................................................................ longihamulus

- Anterior hamulus with anterior branch comparatively short and broad, occupying about a half of anterior hamulus length ( Figs 22, 24, 26 ); basal hamulus tooth broader and forming a triangular lobe........................................... 2

2 Posterior hamulus in lateral view curvilinear, narrowed apically ending in a narrow spatulate lobe; cornua of glans short, branches widely separated apically ( Fig. 27 ); larger species (Abdomen: 46 mm; Hw 37 mm)..................... sinicus

- Posterior hamulus in lateral view hook-shaped, stockier apically ending in a thicker spatulate lobe ( Figs 22, 24 ); cornua of glans long, widely, deeply incised, U- or V-shaped ( Figs 23, 25 ); smaller species (Abdomen: 37–39 mm; Hw 29–31.5 mm)...... 3

3 Lobe of penis vesicle strongly protruded ventrally. Cornua of glans short, U-shaped ( Fig. 23 )................... minimus

- Lobe of penis vesicle short in ventrally. Cornua of glans long, V-shaped ( Fig. 25 )........................... phantoani

Females

1 Vulvar lamina triangularly excavated at apex ( Figs 29, 35 )..................................................... 2

- Vulvar lamina with lobes approximate or narrowly U-shaped ( Figs 31, 33 )........................................ 3

2 Vulvar lamina nearly as long as S9, lobes widely separated apically ( Fig. 29 )............................ longihamulus

- Vulvar lamina half as long as S9 ( Fig. 35 ).............................................................. sinicus

3 Vulvar lamina pointed in apex; occiput with two widely separated, serrated, sharp marginal projections ( Figs 32, 33 )................................................................................................... phantoani

- Vulvar lamina incised apically; occiput with two erect, rounded marginal projections ( Figs 30, 31 )............... minimus

Figures

FIGURES 20–27. Accessory genitalia [20, 22, 24, 26] in lateral view and cornua of glans [21, 23, 25, 27] in ventral view of Ophiogomphus spp. (20–21), O. longihamulus (rearranged from Karube 2014: Fig. 16 e, g); (22, 23), O. minimus (rearranged from Karube 2014: Fig. 18 e, g); (24, 25), O. phantoani sp. nov.; (26, 27), O. sinicus, Cao Bang Province.

FIGURES 28–35. Female occiput [28, 30, 32, 34] & abdominal end [29, 31, 33, 35] in ventral view of Ophiogomphus spp. (28, 29), O. longihamulus (rearranged from Karube 2014: Fig. 16 j, k); (30, 31), O. minimus, Nam Nung Nature Reserve; (32, 33), O. phantoani sp. nov.; (34, 35), O. sinicus (rearranged from Chao 1990: Fig. 10 & Zhang 2019: p. 424).