Drepanosticta emtrai, Dow & Kompier & Phan, 2018

Dow, Rory A., Kompier, Tom & Phan, Quoc Toan, 2018, Drepanosticta emtrai sp. nov. from Vietnam with a discussion of Drepanosticta vietnamica Asahina, 1997 (Odonata: Zygoptera: Platystictidae), Zootaxa 4374 (2), pp. 273-282 : 274-278

Drepanosticta emtrai sp. nov.

( Figs 1–16 , 21 )

Holotype. 1 ♂, Huong Son district , Ha Tinh Province, Vietnam (ca 18.452N, 105.256E), 9 vi 2015, leg. T. Kompier, to be deposited in RMNH.

Paratypes. 1 ♀, in tandem with holotype, to be deposited in RMNH; 1 ♂, Nghe An, Vietnam (18.635N, 105.234E), 10 v 2015, leg. T. Kompier, in coll. Dow; 5 ♂♂, Ba Vi National Park, Hanoi Province, Vietnam (21.084N, 105.370E), 18 vi 2017, leg. T. Kompier; 1 ♂ (semi-teneral), Huay Bordop, Kaew Neua pass area, Bolikhamsai, Laos (18.372N, 105.152E), 670–680 m, 30 iv 2012, leg. M. Hämäläinen, in coll. Dow.

Other material. 1 ♂, Hoa Binh, Vietnam (20.784N, 105.480E), 27 vi 2014, leg. T. Kompier, in coll. Dow, see the Remarks section below.

Etymology. emtrai , a noun in apposition; this word means younger brother in Vietnamese. It is a reference to the slightly smaller size and apparently slightly later date of emergence of the species compared to D. hongkongensis , to which it is very similar and with which it co-occurs on Ba Vi Mountain.

Description of holotype male. Head ( Fig. 1 ). Labium brown and pale greyish. Labrum pale blue, narrowly black along free margin. Mandible bases pale blue, narrowly black along free margin and part way beside genae. Anteclypeus pale blue, postclypeus black. Vertex, frons, occiput and underside of head black, small brownish marks behind antennae bases, immediately anterior of median ocellus (not clearly visible in Fig. 1 because of angle), immediately exterior to lateral ocelli. Vertex relatively broad, ratio of width of compound eye to width of vertex measured at level of lateral ocelli slightly more than ca 0.7. Transverse occipital carina moderately developed. Ocelli whitish. Antenna with scape and pedicel grey, pedicel brown at top, remainder dark brown.

Thorax. Propleuron mostly black and dark brown, paler areas along lower margin ( Fig. 5 ). Anterior pronotal lobe low, largely blue, dark brown to rear and on lateral extremities ( Figs 3, 5 ). Middle pronotal lobe black and dark brown with pair of dorsal blue markings ( Figs 3, 5 ). Posterior lobe black centrally, dark brown with obscure paler areas to sides, where somewhat expanded ( Fig. 3 ). Synthorax: Mesepisternum, mesepimeron metallic black with greenish cast except mid dorsal carina where bronzy black, antealar triangles black, mesostigmal plates greyish brown. Metepisternum and metepimeron mostly dark brown, blue marking on metepisternum, well defined towards wing bases but obscure towards legs ( Fig. 7 ), small yellowish mark immediately above spiracle. Venter of synthorax pale, gentle swelling visible near abdomen ( Fig. 7 ). Mesokatepisternum dark brown, pale adjacent to coxa, metakatepisternum mostly pale. Legs each with coxa, trochanter and femur pale yellowish, femur with narrow, faint, irregular dark stripe along much of lateral extensor surface, dark immediately above joint with tibia. Tibia and tarsi mostly pale with indistinct darker areas, tarsal claws pale brown. Wings: 14 Px (left), 16 Px (right) in Fw, 14 in Hw. Vein ab present, bifurcated. Arculus slightly distal to Ax2. R4 arising slightly distal to subnodus, IR3 joined to it by short stalk. Pterostigma ca trapezoidal with costal side shorter than anal side, dark brownish black with narrow pale border, covering slightly more than one underlying cell.

Abdomen. S1–2 mostly dark brown with poorly defined pale areas lower laterally. S3–7 dark brown, black apically with broad pale basal annulus, smallest on S3. S8 very dark brown, blue dorsal apical mark, pair of small blue marks just basal of this ( Fig. 9 ), basal ca one half of segment with pale area lower laterally ( Fig. 11 ). S9 blue, brown lower laterally. S10 blue, very dark brown laterally. Anal appendages ( Figs 13–15 ) largely dark brown and black, paler areas towards tips of cerci. Cerci almost 3 times length of S10, in lateral view broad, arched up along lower margin with large heel-like subtriangular ventral flap arising abruptly just after half length, apex of this rounded ( Fig. 14 ). Cerci downturned towards apices, these rounded. In dorsal view ( Fig. 13 ) cerci converging gently along outer margin over entire length, interior margins with small rounded interior flap at ca half their length, followed by slightly larger one subapically, neither visible in lateral view. Paraprocts slightly shorter than cerci, in lateral view broad at base, narrowing rapidly, with dorsal hump before half-length, thereafter slightly sinuous, apices brownish. In ventral view ( Fig. 15 ) narrowing rapidly after half-length, in turned at apices; slender subbasal interior tooth visible, directed upwards and to rear; this also visible in dorsal view, and just visible in lateral view.

Genital ligula ( Fig. 16 ). Broad internal fold, terminal segment slender, divided apically into pair of upward directed arms, these turned towards thorax and expanded apically; space between arms concave.

Measurements (mm): abdomen with anal appendages 36, cercus ca 1, Hw 23.5.

Description of female paratype. As male except as noted. Head ( Fig. 2 ). Without small greyish marks behind antennae bases.

Thorax. Blue marks on middle pronotal lobe slightly larger ( Figs 4, 6 ); blue marking on metepisternum smaller, less well defined ( Fig. 8 ). Wings: R4 arising at subnodus in right Hw, very slightly distal to it in left Hw, 16 Px in Fw, 15 Px in Hw.

Abdomen ( Figs 10, 12 ). S8 without blue markings, S9 blue dorsally in apical half, S10 blue dorsally, cerci black, just longer than S10, ovipositor extending to ca level of tips of cerci, mostly dark brown and black with pale apex, styles brown.

Measurements (mm) Abdomen with anal appendages and ovipositor ca 33, Hw 23.

Variation in paratype males. The paratype from Nghe An, Vietnam, is very similar to the holotype, the only significant differences apart from size and vein counts is that S8 only has a small blue apical dorsal mark, that R4 arises at Sn in the left Hw, and that the apical halves of the paraprocts are straight in lateral view, not slightly sinuous. The five males from Ba Vi, Vietnam, have more extensive blue on S8, ranging from three-fourths to almost completely blue, and have the metepisternum completely black. Their paraprocts are all straight in lateral view, although the apex is turned up slightly in two specimens. In the semi-teneral male from Laos the blue marking on the metepisternum is faint, the extensor surface of the femur is extensively dark and there is a welldefined dark stripe on the extensor surface of the tibia. An apical blue dorsal mark is present on S8, but much of the rest of the dorsum has a diffuse, mottled bluish appearance (perhaps this fades in mature specimens).

Measurements (mm). Males: Abdomen anal appendages 35–36.5, Hw 21–22, 15–16 Px in Fw, 14–15 Px in Hw.

Diagnosis. The male of D. emtrai can be separated from all mainland Asian Platystictidae except other members of the D. carmichaeli -group by the characters defining that group, and from the South Asian species of the carmichaeli -group by the coloration of the prothorax and dorsum of the synthorax, which have more extensive pale marks, including antehumeral stripes in D. carmichaeli and D. polychromatica (see Fraser 1933). It is separated from D. hongkongensis by the blue markings on the anterior and middle pronotal lobes of D. emtrai ( Figs 3, 5 ) and by the curvature of the paraprocts in ventral view ( Fig. 15 ), and from D. jurzitzai by the colour of the pterostigma, said to be yellow ochre in D. jurzitzai ( Hämäläinen 1999) , and from all species except possibly D. vietnamica (see below) by the heel-like subtriangular ventral flaps on the cerci ( Fig. 14 ). It is also separated from D. brownelli and D. hongkongensis by having the basal tooth on the paraprocts slender and only just visible in lateral view ( Fig. 14 ), compared with robust and easily visible in lateral view in these two species (see the Discussion). An additional character separating it from D. brownelli is the position of the stripe on the metepisternum, which is centrally placed in D. brownelli but almost reaches the antealar carina in D. emtrai ( Fig. 7 ). The males of the type series at least are also separated from all other species in the carmichaeli -group except D. brownelli by the mostly pale coloured anterior lobe of the prothorax ( Fig. 3 ), which is either entirely dark or with only limited lateral pale marks in the other species. Drepanosticta vietnamica has a much larger, better defined pale stripe on the metepisternum ( Fig. 17 ).

Remarks. The type series comes from three separated locations in Vietnam, one widely separated from the others, and one location in Laos; although only a limited number of specimens has been observed so far, this indicates a rather large range ( Fig. 21 ).

The male from Hoa Binh has been excluded from the type series of D. emtrai because of differences in the anal appendages compared with D. emtrai : the ventral flap on the cerci, whilst prominent, is smaller than in D. emtrai and there is only a single interior flap visible on the cerci in dorsal view. Although the Hoa Binh male may well belong to D. emtrai , there is also a small possibility that it is a distinct species. It is slightly larger than any of the paratypes: abdomen with anal appendages 37.5 mm, Hw 23.5 mm.

Drepanosticta emtrai differs from D. vietnamica as judged from Asahina’s illustrations and description, and from the available paratype, in a number of respects. Both Asahina’s illustration and Figure 20 here show paraprocts only gently inwards curved in their apical half, but they are strongly curved in their apical half in D. emtrai . The cerci appear to have a ventral flap in Asahina’s illustration, but it appears less well developed than that in D. emtrai ; but in the paratype of D. vietnamica there is only a small inward directed protrusion in approximately the same position, visible in dorsal view ( Fig. 19 ), but not in lateral view ( Fig. 18 ). The tips of the cerci are rounded in D. emtrai but appear almost hooked down in Asahina’s illustration of D. vietnamica ; they have a completely different appearance in the paratype ( Fig. 18 ). In D. vietnamica a small but well developed dorsal projection at the point where the upper margin of the cerci turns downward is visible in Asahina’s illustration, a projection is also visible in the paratype ( Fig. 18 ), although it is more easily seen in dorsal view ( Fig. 19 ) where it appears as a flap; but in the same lateral and slightly dorsal view, no structure in the same position is visible in D. emtrai , but there are two inwards directed, shallow, rounded flaps present on the upper inner margin of the cerci, visible in dorsal view ( Fig. 13 ). In D. vietnamica the anterior lobe of the prothorax is stated to be “black with ambiguous pale spots laterally”, figure 2 in Asahina (1997) also shows what appear to be pale marks on the middle lobe and these are also present in the paratype ( Fig. 17 ); the markings on the anterior lobe in the type series of D. emtrai are better defined and more extensive than in D. vietnamica . The pale stripe on the metepisternum of D. vietnamica in both Asahina’s illustration and the examined paratype ( Fig. 17 ) is longer and much better defined that in D. emtrai ( Fig. 7 ). Differences in the colour of parts of the head and the terminal abdominal segments are likely to be due to the preservation methods employed and different ages of the specimens, so are not considered to be reliable here. The type series of D. emtrai comes from a large geographical area in Vietnam from Ha Tinh in central Vietnam and nearby Nghe An and Laos, to Ba Vi Mountain in northern Vietnam. Although the type series displays some variation in outward appearance, notably the extent of the pale marking on the metepisternum and the blue area of S8, the observed variability does not come close to the pattern of D. vietnamica and the shape of paraprocts and cerci is much more constant. Nevertheless, variation cannot be completely discounted as a factor in differences in the markings between D. vietnamica and D. emtrai .

Drepanosticta emtrai was found in Ha Tinh and Nghe An provinces in logged mature forest at seeps that possibly dry up for part of the year. On Ba Vi Mountain, Hanoi, it occurs at seeps under dense forest cover, interestingly preferring almost identical, although possibly slightly less rocky, seeps than D. hongkongensis , which occurs in its close vicinity on the same mountainside. It appears to emerge a few weeks later than D. hongkongensis , but at least on Ba Vi Mountain both species occur in the middle of June.

Figures

FIGURE 21. Distributions of Drepanosticta emtrai and D. vietnamica. Yellow circles: D. emtrai type series; red square: specimen excluded from the type series of D. emtrai (see remarks section under D. emtrai); black circle: D. vietnamica (approximate position of type locality).

FIGURES 1–6. Drepanosticta emtrai. Head: (1) holotype male; (2) paratype female.Prothorax, dorsal: (3) holotype male; (4) paratype female. Prothorax lateral:(5) holotype male; (6) paratype female.

FIGURES 7–12. Drepanosticta emtrai. Synthorax, lateral: (7) holotype male; (8) paratype female. Terminal abdominal segments, dorsal: (9) holotype male; (10) paratype female. Terminal abdominal segments, lateral: (11) holotype male; (12) paratype female.

FIGURES 13–16. Drepanosticta emtrai. Anal appendages and genital ligula of holotype male. Anal appendages: (13) dorsal; (14) lateral; (15) left paraproct in ventral view.(16) Genitalligula, ventral view.

FIGURES 17–20. Drepanosticta vietnamica paratype: (17) head and thorax; (18) anal appendages, lateral view; (19) left cercus, dorsal view; (20) left paraproct,oblique dorsal view.