Rhinagrion hainanensis Wilson and Reels, 2001

This species was described based on the male holotype that collected from Hainan. Latter the female and its larvae was described in detail by Sasamoto et al. in 2011. The species R. yokoii Sasamotoi, 2003 was found from Laos is synonym of this species. It is the second species of the genus that found in Vietnam, the other is R. mima which was found from other South East Asian countries and in Phu Quoc Island, Vietnam as well. 

A medium-small sized damselfly, this species has colourful body with black, cream-emerald, cream-yellowish, turquoise, red-brown and brick-red marking. The head is narrower in width than it of other later damselflies with three ocelli are quite big and close together. The face is unmistakeable with two lateral cream-emerald markings. The thorax is colourful; the dorsum of the synthorax is black with two big cream-yellowish markings while in lateral view, the thorax is change from red-brown to cream-turquoise with black markings. In ventral view, the synthorax and inner side of femora are light-turquoise. The dorsal abdomen segments are red dark brown with cream-yellowish and dark-turquoise marking. Remarkably, at ventral view, the sixth to eighth segments are bright brick-red while they are light orange in the ninth and tenth segments. Their wings are petiolate, hyaline and alway in horizontal position at rest. 

They live in clean, swift and shallow streams in good humid forests of the centre of Vietnam. The colourful body makes the species to be brightening in any views: dorsal, lateral or ventral. They are weak flied insects and usually hide in vegetations that hanging over the water.

Male, lateral view, photographed by Cuong Do, Phu Yen provine

Close up face of male, photographed by Cuong Do, Phu Yen Province

Euphaea masoni Selys, 1879

This species is close to E. guerini and E. hirita, three species are very similar in external structure generally. The damselflies had been mixed with E. guerini as same species but now there are many evidences show that they are three distinct species. 

Similar to its two sister species, they are medium damselflies with dark colours of body and wing generally. The mainly typical characteristic of male individuals of this species is the abdomen without hair or hair stuffs in lateral view. Beside, in dorsal view or upper side of the wings of male, in sunshine and as they open their wings, the hind-wings show its iridescent red flash. Their females are not very special recognized by morphological characteristics with hyaline wings and black body with yellow-greenish markings.

This species somehow is more widespread than the others and have been found over the whole of the country. They live in clear, swift and hemi-shade streams in both disturbed and primary forests. Males protect their territory by fighting and showing their red flash hind-wings and mate with coming females, the later behaviour also use in their courtship. The females are less active and usually perch higher positions.

Male with red flash wings, photographed by Cuong Do, Phu Yen Province

Close up to the face of the male, photographed by Cuong Do, Phu Yen Province

Male with wings are close, showing the blue color of underside, photographed by Cuong Do, Quang Binh Provicne

Under the sunshine, above stream, the male look very colorful with his red wings, photographed by Cuong Do, Quang Binh Province

Heliocypha biforata biforata (Selys, 1859)

Very similar to H. perforata, they are also black and cobalt-bluish marking damselflies. Their wings are narrow like H. perforata but the iridescent areas on the wings are broader. Males of the species are distinct by markings on the synthorax and the abdomen. The abdomen of male is stouter than it of H. perforata, with distinct blue markings on lateral side of each segment. Females have no valuable in identification of the species. Their habitats, territorial and courtship behaviours are very similar to it of H. perforata, but H. b. biforata prefer opened running waters. They are widespread species but distribute locally.

Young male, photographed by Cuong Do, Quang Binh

Thorax marking of full mature male, photographed by Cuong Do, Phu Yen