Risiophlebia guentheri, Kosterin, Oleg E., 2015

Kosterin, Oleg E., 2015, Risiophlebia guentheri sp. nov. (Odonata, Libellulidae) from southeastern Indochina, Zootaxa 3964 (1), pp. 138-145 : 139-144

Risiophlebia guentheri sp. nov.

( Figs. 1, 2 a–h)

Type material. Holotype: ♂, Cambodia, Mondulkiri Province, Dak Dam village environs, a tall grass swamp, 12°25' N 107°19' E, ~ 780 m a.s.l., 16 vi 2014, deposited in RMNH. Paratypes: 2 ♂ paratypes No. 1, in ISEA, and No. 2, in ZMUM), 1 ♀ (paratype No. 3, in RMNH), the same place and date.

Etymology. The species is named in honour of André Günther as a recognition of his studies of Odonata behaviour in Southeast Asia and activities to promote the International Dragonfly Fund.

Description of holotype male. Head: Eyes in life: a distinct brown patch above, extending ventrally at hind margins, the rest grey, gradually turning greenish below, with blackish spots: a large central anterior one and a few smaller ( Fig. 1 a). Rear of head black, hairy. Vertex metallic dark green, top of frons same colour, fading to brownish-black at lower part; postclypeus central part brown; anteclypeus, most of postclypeus and lateroventral corners of frons yellow to form a broad, laterally widening stripe across head with an evenly convex dorsal margin ( Fig. 2 f). Labrum and mandibles black; genae brownish-black. Labium yellow, with distal and inner margins of movable hooks broadly black ( Fig. 2 f).

Thorax: metallic dark green with a citron-yellow pattern ( Fig. 2 a); green lustre most saturated at mesepisternum but disappearing at venter of synthorax and metepimeron where ground colour becomes dark brown.

Prothorax: anterior lobe black at base, bright yellow in anterior part; medial lobe black with small yellowish spots at posterolateral corners, set with hairs; posterior lobe large, prominent, directed posterodorsally for half right angle to body axis, strongly broadening from base, rounded at sides, with an almost straight hind margin and a central linear dimple that is bright yellow, set with very long hairs at free margin.

Synthorax set with small light hairs in front and below. Mesepisternum with a dorsally elongate and pointed yellow spot at ventrolateral corner; it continues as a broad yellow stripe at inframesepisternum and then to a narrower stripe on mesocoxa ( Fig. 2 a). The resulting subvertical band twice bent at blunt angles at border of the three mentioned sclerites. A broad vertical yellow stripe goes along border of mesepimeron and metepisternum, embracing spiracle, and continues on inframetepisternum, bent at its border at a blunt angle directed ahead ( Fig. 2 a). Mesepimeron with a broad yellow stripe narrowing below and occupying most of its area, leaving dark only anterior margin and dorsoposterior corner ( Fig. 2 a). Poststernum yellowish with dark borders. Sclerites in antealar sinus and between wings yellow.

Legs black but all coxae with yellow stripes along them, protrochanter yellow and profemur ventral side yellow for 2/3 of its length ( Fig. 2 a).

Wings ( Fig. 2 m) hyaline, with an amber tint at bases, stronger between ScP and RA and between CuA and AA, gradually disappearing to level of triangles. Ax: 11 on FW, 10 on left and 9 on right HW; Px: 7 on left and 6 on right FW, 6 on left and 7 on right HW. Crossveins between RA and RP from bridge to nodus: 9 on FW, 6 on left and 7 on right HW. Cubitoanal field with 1 crossvein on both wings. Cells between RP 3-4 and MA: 17 on FW, 14 (the last two one above another) on hind wing. Discoidal field: 15 cells (the first 12 in one row) on left FW, 17 cells (the first 2 one above another, then 11 in one row) on right FW. Anal loop open, with 7 cells on left and 9 cells on right HW. Pt dark brown, with longitudinal bordering veins swollen, below contacting 2 crossveins.

Abdomen: S1 and S2 drastically expanded ventrally, with S3 involved in this expansion, with its anterior margin in profile view thrice as high as posterior margin ( Fig. 2 a). Rest of abdomen extremely slender and arched bow-like, but S8–10 moderately expanded ( Fig. 1 a). Ventral parts of S2 and S3 tergites with long yellowish hairs ( Fig. 2 c–e); otherwise abdomen with very fine light pubescence, stronger on ventral parts and at S8 – 10. End of S10 and appendages with quite dense medium long light-brownish hairs. Ground colour blackish-brown on S1–3, turning black distally. Yellow markings as follows: S1 with a broad ring along posterior margin; either side of S2 with large isolated oval spot, just above secondary genitalia; S3 on either side with long vertical bars on either side, bordered with seams and close to anterior margin but separated from it, and small patches at tergite ventral margins; S4 and S5 with small rings, interrupted at sides, at anterior margins; S6 with a dorsal transverse spot at anterior margin, corresponding to upper ring fragment of S4–5; S7 with an elongate dorsal spot broad in front and pointed at apex but split by a median line of ground colour, which occupies about 2/5 of segment length. In addition, there are tiny yellow dorsal dots at distal margins of S6–8.

Epiproct about 0.82 times as long as cercus ( Fig. 2 g, h). Ratio of lengths of cercus, epiproct and S 10 in profile view is very close to 3:2.5:1. In profile view, cercus somewhat S-like curved with raised and acutely pointed apex, expanded to a large ventral subtriangular projection situated at about 0.45 cercus length, apex rounded with coarse margins but without strong teeth ( Fig. 2 g). Epiproct ends at 2/3 distance between ventral projection and apex of cercus. Epiproct dorsal side very slightly and evenly concave and ventral side evenly convex ( Fig. 2 g). In dorsal view, cerci gradually narrowing at proximal 1/4 and tapering to pointed apices; epiproct moderately notched at apex ( Fig. 2 h).

Accessory genitalia prominent ( Fig. 2 c). Posterior hamulus with a very robust, curved anterior hook and a nearly right angle between ventral hollow and posterior side, which is slightly concave ( Fig. 2 c). The hollow, as limited by an imaginary line connecting anterior angle and hook tip, half as deep as long. Vesica spermalis halfdome-like, slightly overlapping with posterior hamulus anterior margin. Genital lobe small and narrow but rounded. Accessory genitalia black, but hamulus ventral hollow margin and top of vesica spermalis yellowish-grey ( Fig. 2 c).

Measurements (mm): Hind wing 23, abdomen without appendages 22, pterostigma 2.4 on FW and 2.6 on HW.

Variation in male paratypes. Both male paratypes are identical to the holotype in most respects including size. Paratype No. 1 looks subteneral. In both, the light spots at posterolateral corners of the pterothorax medial lobe are vestigal.

Wing venation varies as follows. Ax: 10–11 on FW, 9–10 on HW; Px: 6–7 on FW, 6–8 on HW. Crossveins between RA and RP from bridge to nodus: 9–10 on FW, 7–8 on HW. Cells between R3-4 and MA: 17–18 on FW, 15–16 on HW. FW discoidal field: 15–18 cells. Anal loop with 9–10 cells.

In paratype No. 1, yellow spots on S2 are prolonged dorsally to contact the tergite anterior margin, hence separated from the yellow ring on S1 only with a black rim along the margin. In both paratypes, S4–6 have entire anterior yellow rings. The dorsal spot on S 7 in paratype No. 1 is short and occupies ca 1/5 of the tergite length, while in paratype No. 2 it occupies half of its length.

In paratype No.1, the hollow of the posterior hamulus is shallower, ca 45% as deep as long, while the hamulus posterior margin is slightly convex and concave only at the base ( Fig. 2 d).

Female. Resembles the male ( Fig. 1 b–c).

The head is missing in the only female specimen; in the photo in nature, the upper margin of the yellow stripe across the face looks uneven at postclypeus. Yellow stripe on inframesepisternum and lateral yellow stripes of synthorax slightly broader than in male; antehumeral stripe on mesepimeron longer and more attenuated at apex.

Wings as in male, with somewhat stronger amber tint at bases. Ax: 11 on FW, 10 on HW; Px: 8 on left and 7 on right FW, 7 on HW. Crossveins between RA and RP from bridge to nodus: 9 on FW, 8 on left and 7 on right HW. Cubitoanal field with 1 crossvein on both wings. Cells between R3-4 and MA: 20 on left and 18 on right FW, 16 on left and 17 (the last two one above another) on right HW. Discoidal field: 18 cells on left and 17 on right FW, with the first 2 one above another, then 11 in one row. Anal loop 10-celled.

Abdomen shaped as in male but somewhat thicker. Ventral expansion of S1 – 3 smoothly rounded and looks less expressed. Abdominal yellow markings as follows: S1 with a posterior yellow ring; S2 on both sides with broad vertical yellow spots in ventral parts that form a united band with S1 ring (interrupted with a narrow black margin of S1); S3 with broad vertical lateral stripes, truncated above, as in male; ventral margins of S3 and S4 tergites margined with yellow; S4 – 6 with vestigial dorsal stripes along anterior margin; S7 with a large elongate dorsal spot occupying ca 4/5 of segment length, bifid for about 2/5 of its own length; S7 and S8 with yellow dorsal dots at their distal margins.

Valvular lamina scarcely developed, looks like a somewhat raised margin of S8 with a gentle dimple at middle. Cerci simple and short.

Measurements (mm). Hind wing 25, abdomen without appendages 24, pterostigma 2.5 on FW and 2.8 on HW.

Short diagnosis. A relatively large Risiophlebia , (HW 23 mm in males, 25 mm in females; 9–10 Ax). Males with a not erected posterior angle of the posterior hamulus, so that the incision between it and the hamulus hook is shallow, about half as deep as long. Ventral projection of male cercus coarse but without strong teeth; epiproct more than 0.8 as long as cercus, protruding for 2/3 of distance between ventral tooth and apex of cercus.

Differential diagnosis. The new species was compared with R. dohrni , namely with its original description ( Krüger 1902), a detailed redescription by Ris (1909) and figures therein, three male specimens from Sarawak and Brunei kindly provided by Rory Dow and a photo of the secondary genitalia of a male from Brunei kindly provided by Albert G. Orr. The provenance of the above mentioned specimens is as follows: 1 ♂, W Sarawak, Mulu area, secondary swamp forest, 18 iv 2005; 1 ♂, Sarawak, Kuching, UNIMAS Campus, Bahagian Samarahan, peat swamp forest, 24 i 2006 ( Fig. 2 i, k–l); 1 ♂, Brunei, Belait District, Kuda-Belait road, peat swamp forest, 27 v 2013 ( Fig. 2 j).

The new species is about 20% larger than R. dohrni , which has HW 18–20 mm long in males and 19–21 mm in females and abdomen of 19–20 mm in males and 18 in females ( Krüger 1902; Ris 1909; Orr 2005; Tang et al. 2010). The three examined males had HW length 19.5–20 mm and abdomen length 17.5–18.5 mm. The number of antenodal crossveins (Ax) is greater accordingly, 10–11 on FW and 9–10 on HW in R. guentheri versus 8–9 on FW and 7–8 on HW in R. dohrni (in the studied specimens, 8 in one case and 9 in five cases on FW and 7 in two cases and 8 in four cases on HW).

The strongest morphological differences are found in the accessory genitalia and anal appendages.

In R. dohrni the posterior prominence of the posterior hamulus extends above the level of the ventral incision to form a blunt tooth rising to about 3/4 of the level of the anterior hook ( Fig. 2 i–j). As a result, the incision between the apices of the hook and prominence is about 90% as deep as long. In R. guentheri the posterior projection is close to being just a rounded right angle between the ventral and posterior margins of the hamulus, embracing an incision between its apex and the hook apex about 45–50% as deep as long ( Fig. 2 c–e).

In R. dohrni the cercus is relatively much longer, the ratio of lengths of the cercus, epiproct and S 10 in profile view being ca 4:2.7:1 ( Fig. 2 g) (3:2.5: 1 in R. guentheri , Fig. 2 k). That is, in R. dohrni the epiproct is 0.70 as long as the cercus and extends for 1/3 of the distance between the ventral projection and apex of the cercus ( Fig. 2 g), while in R. guentheri it is 0.82 as long as the cercus and extends for 2/3 of this distance ( Fig. 2 k). In ventral view, the epiproct of R. dohrni looks truncated, at the apex exactly twice narrower than its widest place, with a shallow triangular notch ( Fig. 2 h), while in R. guentheri it looks more attenuated and narrowed, at the apex exactly thrice narrower than its widest place and with a narrow, more rounded notch ( Fig. 2 l). An important difference concerns the cercus ventral projection: its margins are coarse in R. guentheri but lacks distinct teeth, while in R. dohrni its basad slope bears three strong teeth ( Fig. 2 k).

There are some additional minor differences. The abdomen in males of R. guentheri seems to be less curved than in R. dohrni . The abdominal yellow pattern in the new species is somewhat more restricted than in R. dohrni : the anterior lateral yellow bars on S3 do not merge on the dorsum (merged in specimens of R. dohrni ). The anterior yellow rings at S4–6 are interrupted at the sides in the holotype and the mature paratype but entire in the teneral paratype and mature specimens of R. dohrni . The subventral yellow spots on S2 do not proceed irregularly along anterior segment border in the holotype and the mature paratype but proceed in the teneral paratype of R. guentheri and specimens of R. dohrni . The basal amber, well expressed in the new species, is reduced to traces in R. dohrni . However, such coloration characters are variable and not reliable in libellulids.

The size and the correlated venational character (the Ax number) is so far the only diagnostic character found in the female.

Habitat. In general, the area between the province capitol Sen Monorom and the Vietnamese border is an elevated (500–900 m a.s.l.) hilly land covered by grassy savannah transitioning to semi-evergreen forest in valleys. The type locality is situated in the vicinity of Dak Dam village, the ‘capitol’ of Pnong (Bunong) minority, very close to a small river, at ca 780 m a.s.l. R. guentheri were found to be rather abundant but in a very restricted area (ca 100 x 50 m) of a swamp with with thickets of a tall (up to 3–3.5 m high) sedge ( Cyperus sp.), large ferns, shrubs (mostly Melastoma ) and sparse trees ( Fig. 3 ). Individuals of R. guentheri perched on tall sedges mostly at about 2.5 m high. When startled, they flew for short distance and landed on the tall sedges or melastomes again. There were some small and very shallow pools with dark water near the tall sedge thickets where these dragonflies could breed, but they were not observed associated with these pools. No behaviour was observed as described by Orr (2005: 89) for R. dohrni as follows: “males perch in sunspots over small pools or sluggish channels.” Perhaps the individuals found were not mature enough to breed.

At the same swamp I collected a male of a rare libellulid Amphithemis curvistyla Selys and observed such common ones as Neurothemis fluctuans (Fabricius) (many immature males), N. fulvia (Drury) (a male), Orthetrum chrysis (Selys) (several males), O. luzonicum (Brauer) (many males), and Tetrathemis platyptera Selys (a male).

The habitat of the new species, a sedge swamp, is generally the same as that of R. dohrni . It should be noted, however, that it was not peaty (the preferred habitat of R. dohrni ) and was situated at almost 800 m above sea level, while R. dohrni is considered as a lowland species ( Orr 2005).

Distribution. Central Plateau (Central Highlands) of the Annamese Mountains in East Cambodia (recorded in Mondulkiri Province) and, most probably, South Vietnam (putatively recorded in Lâm Đồng Province).

Figures

FIGURE 2. Details of Risiophlebia guentheri (a – h, m) and R. dohrni (i – l); a, c – m—males, b—female; a, c, f – h, m—holotype, d—paratype 1, e—paratype 2 of Risiophlebia guentheri; i, k – l—male of R. dohrni from Sarawak, Kuching, j—male of R. dohrni from Brunei, Belait; a – b—thorax and abdomen base in lateral view; c – e, i – j—secondary genitalia in lateral view; fhead in frontal view; g, k—S 10 and appendages in lateral view; h, l—the same in ventral view; m—wings. Not to scale.

FIGURE 3. Habitat of Risiophlebia guentheri at the type locality: Cambodia, Mondulkiri Province, Dak Dam village environs, a tall sedge (Cyperus sp.) swamp.