A revision of the systematics and distribution of the damselfly genus Prodasineura Cowley, 1934 (Odonata: Zygoptera: Platycnemididae) in Vietnam with description of two new species

Eight species of the genus Prodasineura Cowley, 1934 are recorded from Vietnam, including two newly described species: Prodasineura lancastrei sp. nov. and P. kong sp. nov. from north and central Vietnam. All species recorded are illustrated, including figures of morphological structures, and distribution maps and keys to the males and females are provided. We consider the record of P. laidlawi (Forster in Laidlaw, 1907) a misidentification and exclude it here.


Introduction
Damselflies of the genus Prodasineura Cowley, 1934 were placed in the family Protoneuridae before Dijkstra et al. (2014) rearranged its members into the family Platycnemididae following molecular phylogenetic research. These are very slender damselflies, the males are usually black, striped with blue, red or yellow. The pattern of the male synthorax and abdominal tip and the morphology of the appendages are diagnostic characters for species of this genus. The male cerci are hammer-like with a pointed apex; the paraprocts are broad at base and tapering abruptly to a rounded tip. Females of Prodasineura are similar in shape and thoracic colour pattern. In females, the posterior pronotal lobe of the prothorax is characteristically well developed and offers good diagnostic characters for their separation. These damselflies are usually found on slowly flowing water with a sandy bottom, near open streams in pristine, secondary forests or on small river branches in the lowlands.

Diagnosis
Male characterized by black body with some pale markings on mesepisterum, metepimeron of synthorax  which disappear when reaching maturity; abdomen, appendages entirely black . Females similar to other species of genus in appearance. Prothorax black with two lateral yellow stripes extending to lateral margin of posterior pronotal lobe (Fig. 1E). Posterior pronotal lobe of prothorax strongly curved upward in lateral view, posteriorly bearing two converging processes (Fig. 5A). Abdomen black except for thin lateral whitish stripe running from S1 to S9 (Fig. 1G).

Distribution
Vietnam (

Diagnosis
Male black with bluish stripes on head, thorax, abdomen and anal appendages (Figs 2A,. S8 with two small distinct spots (in Dong Nai specimens, Fig. 3A) or entire dorsal stripe which extends posteriorly (in Quang Binh specimens); blue marking covering most of S9, gradually narrowing at base thus forming blue triangular-shaped spot; dorsal S10 blue, lateral-ventral black (Fig. 3A). Cerci dorsally entirely blue; paraproct blue, black apically . Female similar to male in shape, body colouration; pale elements are yellowish (Fig. 2B). Posterior pronotal lobe of prothorax with separate ear-like process on each side (Figs 4B, 5D-E).

Distribution
Vietnam (Fig.   Images not to scale.

Diagnosis
Male distinctive with large blue oval markings on mesepisterum (Fig. 2C); dorsum of S9 with rounded blue spot (Fig. 3C), versus only very small blue dot in P. hoffmanni (Fig. 3G) or large marking on S9, two smaller dots or stripe on S8 in P. coerulescens (Fig. 3A). Posterior pronotal lobe of female prothorax similar to that in P. hoffmanni, with short horn on each side, two rounded processes posteriorly; lobes not converging (Figs 4D-E, 5C).

Distribution
Vietnam (

Diagnosis
Male resembling P. coerulescens with blue markings on head, thorax, abdomen, appendages. Male easily distinguished from P. coerulescens by markings of abdomen tip: small blue dot on S9 and S10 blue on dorsum ( Fig. 3G-H) while S8-10 largely blue in P. coerulescens . Female very similar to male in body colouration, including green tones ventrally; antehumeral stripes narrow (Fig. F). Structure, shape of female posterior pronotal lobe of prothorax similar in these species but lobes converging, enclosing roundish space, in P. hoffmanni (Fig. 5F), not converging, enclosing semicircular space, in P. doisuthepensis (Fig. 5C). Images not to scale.

Remarks
This species was described from Mondulkiri Province in Cambodia close to the border of Vietnam (Kosterin 2015) and has been recorded from Lam Dong and Dong Nai Provinces of South Vietnam (Kosterin 2016). Yokoi & Souphanthong (2014) provided colourful photos of two bluish Prodasineura

Diagnosis
In Vietnam, males of both P. croconota and P. verticalis with large egg-shaped orange markings on dorsum of synthorax but those in P. croconota shorter and broader than in P. verticalis (Fig. 6C-D), less saturated in colouration. In males of P. croconota, head with two small spots dorsally adjacent to ocellar tubercle (Fig. 6A) but with large transverse stripe in P. verticalis (Fig. 6E). Cerci in P. verticalis mostly black except for indistinct basal yellow stripe dorsally  while cerci dorsally entirely yellowish or bluish in P. croconota ; ultimate segment of genital ligula of P. verticalis acute at apex (Fig. 7F) but blunt in P. croconota (Fig. 7C). Posterior pronotal lobe of prothorax of female P. verticalis characterized by two thin, long horns  while robust and short in P. croconota (Fig. 13A-B).

Remarks
Bui (2007) recorded Elattoneura sp. at Phu Quoc Island, which subsequently was reidentified as a Prodasineura sp. by Do et al. (2011). Based on examination of specimens, it was identified as P. verticalis by Kompier (2019). This paper confirms the identification of the Prodasineura species from Phu Quoc Island recorded in Bui (2007), Do et al. (2011) and Kompier (2019) was P. verticalis. Asahina (1997) presumed that a male from Mai Chau of Hoa Binh Province (northern Vietnam) was probably P. verticalis (see in Asahina 1997: 20, figs 7-8). However, according to Asahina, this was "a pale bluish striped, black-bodied species", which is not consistent with P. verticalis with orange stripes. Asahina's drawing shows a species with thin antehumeral stripe, which may well be Prodasineura coerulescens, which occurs also in the similar lowland limestone forest in Quang Binh Province, rather than P. hoffmanni (see in Asahina 1997: 20, figs 7-8) which is recorded further south from primary forest of the Central Highlands or evergreen forests in Cat Tien National Park. Asahina's (1997) male should be re-examined to establish its identity with certainty.

Remarks
Asahina (1969) reported P. laidlawi from Dinh Quan District of Dong Nai Province, but included no figures of its structures. Other studies in Cat Tien National Park and Dinh Quan District of Dong Nai Province record the similarily marked species P. coerulescens but not P. laidlawi (Do & Dang 2007;Kompier 2019; this study). We suggest that the male of P. laidlawi as identified by Asahina (1969) was probably P. coerulescens. The occurence of P. laidlawi in Vietnam is also unlikely given the known range of P. laidlawi, which has been reported from Malaysia (Orr 2005) and Thailand (Asahina 1983).

Diagnosis
Male very similar to those of P. croconota and P. verticalis but differing in following characters: large transversal stripe on dorsal surface of head (Fig. 9A), interrupted centrally, not connecting, covering anterior ocellus as in P. verticalis (Fig. 6E) (with small spots in P. croconota, Fig. 6A); antehumeral stripe narrow (Fig. 9A), not large shield-shaped as in P. croconota and P. verticalis (Fig. 6C-D). In fully mature specimens, paraprocts of P. verticalis entirely black (Fig. 7D-E) while yellow apically in P. kong sp. nov. (Fig. 9C). Cerci distinctly different in shape (Fig. 9C, E). Cerci, paraprocts yellow or bluish (except for black ventral side of cerci and base of paraprocts) in P. croconota (Fig. 7A-B). Structure of posterior pronotal lobe of female prothorax somewhat similar to that in P. croconota (Fig. 13A, D) with two short, robust horns, unlike two long horns of P. verticalis (Fig. 13G-H). Prodasineura kong sp. nov. similar to P. lancastrei sp. nov. by sharing same character of narrow antehumeral stripe on male synthorax, but males differ very much in structure of appendages, wing colouration. Females differ in structure of posterior pronotal lobe (see Diagnosis for P. lancastrei sp. nov.).

Etymology
The new species is named after the giant ape Kong since it was discovered at the filming location of the American monster film "Kong: Skull Island", in Tu Lan Caves System of Quang Binh Province, central Vietnam. A noun in apposition. Head. Labrum, mandible, genae, anteclypeus dark red except for upper genae; upper genae black. Space between eye margins, genae shining black (Fig. 9A). Frontal, dorsal surfaces of head, including postclypeus, antennae, matt black except for large orange transverse stripe running from eye margins across anterior ocellus (Fig. 12A).
tHorax. Prothorax black with orange markings on distal margin of each pronotal lobe as follows: thin stripe on anterior lobe, small spots on posterior lobe, large oval spot on middle pronotal lobe (Fig. 9A). Propleuron entirely black. Synthorax black with narrow orange antehumeral stripe; two other distinct stripes: paler orange on metepisternum, yellowish on lower margin of metepimeron (Fig. 9A).
abdoMen. Mostly black except: yellow triangular spots on lower margins of S1; yellowish bands on ventro-lateral surfaces of S2; small spot on anterior margin of S3, whitish spot on dorsal anterior margin of S4-7; S8-10 entirely black (Fig. 14A).
anaL appendages. Typical of members of genus Prodasineura with cerci hammer-like shaped; paraprocts broad at base, tapering abruptly to rounded tip; cerci black excepted tip dark yellowish; paraprocts black at base; remain yellowish ( Fig. 9C-D).
genitaL LiguLa. Latero-apically with two robust flagella with pointed tips; subbasal shorter flagellum, expanding apically as rounded lobe (Fig. 10B).  over postclypeus to level of base of antennae; antennae black; anteclypeus dark yellowish; postclypeus yellow with two separated black spots, black stripe centrally. Antennae black except for second segment, yellowish anteriorly. Front, rear of head black with large transverse yellowish stripe at level of anterior ocellus.
Legs. Coxae yellowish with large outer black spot; trochanter yellow with flexor side black; tibia, tarsus, claws black.
abdoMen Figs 11C, e, 14b. Black with yellowish pattern: S1 with heart-shaped spot on lateral sides; S2 with narrow yellowish stripes along lower margins; ventro-lateral halves of S3-6 brown-yellowish with oval yellowish spot on anterior margin of each segments; S7 dark brownish and S8-9 black with yellowish stripe on lower margin; dorsal side of S8 with oval yellow spot posteriorly but extending to mid-dorsally on S9; lower margin of S10 black but with yellowish marking dorsally (Fig. 11C).

Variation in male and female paratypes
Paratypes from Bac Kan with some orange on dorsum of cerci; male from type location with incomplete transverse band between compound eyes over anterior ocellus. Male from Cao Bang with small orange spot on posterodorsal corner of propleuron. Other male paratypes from type location provided no significant differential features from holotype male. Compound eyes bright red in living male (Fig. 15A). Stripes on male synthorax bright orange in life (Fig. 15A), but stripe on lower margin of metepimeron becoming yellowish after acetone treatment in holotype (Fig. 9A).

Habitat and ecology
The new species was collected in Quang Binh from an open stream (about 3-6 m wide) with fast running water a low limestone mountain area (Fig. 16B). This species usually flies over the surface of water, fighting with two other species of Prodasineura present, for occupation of the habitat near the border of the stream, the blue P. coerulescens and the dark P. autumnalis.

Diagnosis
Differing from most other congeners and all Vietnamese species of Prodasineura by darkened apical wings (Fig. 14C) in male and morphology of posterior pronotal lobe with three flattened horns in female (Fig. 13E-F). In Vietnam, P. lancastrei is superficially most similar to P. kong by sharing the same thin antehumeral stripe on the male synthorax (Fig. 9A-B), but differing by the following characters: in male, transverse band on dorsal head of P. lancastrei narrow (Fig. 9B), wider in P. kong (Fig. 9A); appendages of P. lancastrei mostly black (Fig. 9E-F), paraprocts yellowish apically in P. kong (Fig. 9C-D); cerci of P. lancastrei (Fig. 9E) in lateral view not pointed, ventral expansion convex along posterior margin as opposed to concave in P. kong (Fig. 9C). Female of P. lancastrei differing by three horns (Fig. 13E-F) in stead of two short, robust horns in P. kong (Fig. 13C-D).

Etymology
This species is named after Mr. Luis de Lancastre (born on 20 December 1990) in appreciation of his financial aid for our fieldwork. A noun in the genitive case.    nov., P. autumnalis (Fraser, 1922) and P. croconota Ris, 1916 occur, in Pu Mat National Park. C. Open limestone stream in Tan Hoa Commune, Minh Hoa District of Quang Binh Province with three species: P. autumnalis, P. kong sp. nov. and P. coerulescens (Fraser, 1932) coexisting. D. Habitat of P. hoffmanni Kosterin, 2015 and P. autumnalis in Mang Canh, Kon Plong District of Kon Tum Province.  Head. Labrum dark red with black dot medially. Mandibles yellow, pattern extending to level of postclypeus. Anteclypeus dark red, postclypeus matt black (Fig. 9B). Antennae entirely black. Front matt black except for complete narrow transversal reddish stripe running from eye margins, encompassing anterior ocellus. Rear of head entirely black (Fig. 12C).
tHorax. Prothorax black, orange markings as in Fig. 9B; distal margin of anterior, posterior pronotal lobe with small spot, middle of pronotal lobe with large oval spot. Propleuron entirely black. Synthorax black, on each side with narrow orange antehumeral stripe, two other distinct stripes: reddish one on metepisternum and yellowish ones on lower margin of metepimeron (Fig. 12C).
genitaL LiguLa. Typically shaped for Prodasineura species, two robust flagella lateroapically, extending posteriorly, pointed at tip, bearing subbasal shorter flagellum, which expands apically as rounded lobe (Fig. 10D). Head. Labrum, mandibles, genea, anteclypeus yellowish except for black spot beneath lateral side of mandibles, border of genae black, two separated black spots on anteclypeus; this pattern over postclypeus at level of base of antennae (Fig. 11B). Postclypeus, antennae entirely black. Front, rear of head black, obscure tiny transverse yellowish stripe at level of anterior ocellus (Fig. 12D).
Legs. Same as male.
abdoMen. Black, following pattern: S1 with two oval yellowish spots; S2 with narrow yellowish stripe along lower margin; S3-6 with dark reddish stripe along lower margin, oval yellowish spot on anterior segments, larger spot at about ¾ of each segment length (Fig. 14D); S7-9 black with yellowish stripe on lower margin; S10 black with oval yellow spot dorsally (Fig. 11D, F).

Variation in male paratypes
Two paratype males having yellowish compound eyes due to acetone treatment for preservation, other features of paratype specimens showing no significant differential features from holotype male. Compound eyes bright red in living males (Fig. 15B).

Habitat and ecology
The new species was found in a densely vegetated, very narrow (about 1 m width) branch (Fig. 16C) of a shaded, shallow, narrow (about 1-3 m width) and rocky forest mountain stream with slow running water and a sandy bottom. Two other species of Prodasineura (P. autumnalis and P. croconota) occurred in the same stream with P. lancastrei sp. nov.

Key to the males and females of Prodasineura species from Vietnam
Males of all Vietnamese species of Prodasineura can be separated into two main colourational groups (except for the sole black synthoracic species P. autumnalis) based on the colouration of the male thorax: the blue group (including P. coerulescens, P. hoffmanni and P. doisuthepensis) and the orange group (including P. croconota, P. verticalis, P. kong sp. nov. and P. lancastrei sp. nov.). 4. S8-10 largerly blue, paraproct with blue marking (Fig. 3A-B) .........P. coerulescens (Fraser, 1932) -S9 with a small blue dot, S10 largely blue, paraproct entirely black (Fig. 3G-H)  unique among species of Prodasineura but of the same shape as in the current species of Elattoneura and Disparoneura. The colouration, especially the entirely bright-red eyes, of P. lancastrei (Fig. 15B) comes closest to E. atkinsoni Selys, 1886 but the darkened wings of the male suggest some proximity to Disparoneura, especially D. apicalis (Fraser, 1924) (O. Kosterin pers. comm.). The relationships between the numerous Asian species currently attributed to these two genera Prodasineura and Elattoneura are poorly understood (Dijkstra et al. 2014;Kosterin 2015). Prodasineura lancastrei obviously appears to be more related to Elattoneura atkinsoni or Disparoneura apicalis than to any species of Prodasineura, irrespective of its generic attribution. However, in spite of the anal bride being unreliable for generic subdivision as an evolutionary flexible structure, we decided to describe this new species under the genus Prodasineura as formally fitting its current definition. It should also be noted that the central horns in the female prothorax of P. lancastrei  are unusually structured for all three genera Prodasineura, Elattoneura and Disparoneura which possess only paired structures and no central processes.