Planaeschna crux Kompier & Karube & Futahashi & Phan 2021, sp. nov.

7. Planaeschna crux sp. nov.

(Figs 10, 11A–E)

Holotype. ♂, Pia Oac NP, Cao Bang Prov. (N 22.597, E 105.888), 3-X-2015, TK leg.

Paratypes. 1 immature ♀, Tu Le, Yen Bai Prov., 20-V-2014, S. Sano leg.; 1 ♀, Pia Oac NP, Cao Bang Prov., 4- X-2014, TK leg.; 1 ♀, Tu Le, Yen Bai Prov., 15-V-2015, TK leg.; 3 ♂♂, Tu Le, Yen Bai Prov., 30-VI-2015, TK leg.; 1 ♂ 1 ♀, Pia Oac NP, Cao Bang Prov., 12.IX.2015, TK leg.; 1 ♂ 1 ♀, Tu Le, Yen Bai Prov., 15–16-IX-2015, Q. T. Phan leg.; 3 ♂♂ 4 ♀♀, location, date and collector as holotype; 1 ♀, Tu Le, Yen Bai Prov., 10-VII-2016, TK leg.

Etymology. The specific name “ crux ” is Latin for “cross” and refers to the “disjoined cross” pattern on the dorsum of S2. A noun in apposition.

Description of holotype (Figs 10A, 10D, 11A, 11C–E).

Head (Fig. 10D). Labium yellowish brown, base of mandibles and labrum yellow, anteclypeus yellowish brown, postclypeus greenish yellow, more yellow along lower margin and with two brownish dimples, covered in sparse dark hairs.Antefrons greenish yellow, yellower on central lower part, and browner towards the somewhat raised top, covered in sparse dark hairs. Postfrons dark brown, covered in denser dark hairs. Antennae dark brown. Vertex and occiput black. Compound eyes bluish-green, yellow at lower posterior margin.

Thorax (Figs 10A, 11C). Prothorax brownish. Pterothorax dark brown with green or yellow-green markings as follows: two green broad dorsal stripes on the mesepisternum and with green markings on the antealar sinus (Fig. 11C), mesepimeron dark brown along humeral suture, but largely covered by yellowish green broad lateral stripe. Mesinfraepisternum yellowish green. Metepisternum with green triangle near base of wing, metepimeron mostly greenish yellow. Venter yellowish green. Legs including spikes and claws blackish brown, but inside of anterior femur pale yellow for proximal half. Base of fore and middle femora orange-brown.

Wings hyaline, with black veins and some amber at bases as far as first Ax and anal triangle. Nodal index: 16–22:22–16/18–15:15–18; Pt blackish brown covering 3–3.5 underlying cells in FW and HW. Triangle 3-celled in FW, 3–4 celled in HW. Anal triangle 3-celled. Anal loop 5–6 celled.

Abdomen (Figs 10A, 11A) blackish brown with markings as follows: S1 with a yellowish green PL spot. S2 laterally with yellow auricle surrounded by yellow-green, yellow spot at posteroventral corner and triangular spot laterally at posterior margin, dorsally (Fig. 11A) with disjoined cross formed by two slender green triangular MD spots with apices pointed outward, a slender green triangular AD mark with the apex pointing posteriorly and a thin mid-dorsal line extending from a green line along the posterior margin. S3 with large yellow AL mark, two triangular green MD and PD spots and a small yellow PL spot. S4–7 with green MD spots, S4 and S8 both with a small yellow ML spot, S8–10 otherwise black.

Secondary genitalia apical segment of vesica spermalis of usual type with two globular spheres partly separated by apical cleft and with ears at base.

Anal appendages (Fig. 11D–E) cerci and epiproct black, cerci in dorsal view twice as long as epiproct, with prominent dorsal ridge over apical two-thirds, paddle-shaped, with inward lateral expansion starting just anterior of middle, in lateral view slightly curved upward, tipped with a small tooth. Epiproct elongated triangular with small apical notch in dorsal view, in lateral view widening in proximal half before tapering in apical half.

Measurements (in mm). HW 40.5; abdomen incl. appendages 45.5.

Variation in male paratypes. Paratypes are very similar to the holotype. Immature males (Fig. 10B) have yellow markings and lateral spots in the middle of abdominal segments S4–7, and clearer MD spots on S8. Lateral spots on S1 present in immature males are maintained in some mature males. Ax vary 19–24 in FW, 14–18 in HW, Px vary 13–20 in FW, 16–22 in HW. Anal loop 5–8 celled, triangle in FW 3–5 celled, in HW 4-celled. Pt covering 2–3 cells.

Measurements (in mm). HW 40.5–43.0; abdomen incl. appendages 45.0–47.3.

Description of female paratype (Fig. 10F). As holotype male, unless specified.

Head. Postfrons brown.

Wings more amber at base, extending to the third Ax. Nodal index 17–23:25–16/20–17:18–19, triangle in FW 5-celled and in HW 4–5 celled, anal loop 7–8 celled, Pt covering three cells.

Abdomen (Fig. 11B). As holotype, but lower half of S2 greenish yellow and dorsal pattern S2 somewhat different, with marking along posterior margin not angular, but oval and MD spots smaller (Fig. 11B). S3 with ventral anterior half all yellowish, S4–8 with kidney-shaped yellow AL spot, becoming progressively smaller towards S8.

Anal appendages. Cerci and ovipositor black, cerci nearly as long as S9.

Variation in female paratypes (Fig. 10C). Little variation, amber in wing extending to whole of median space, and postfrons dark brown in some individuals, like male. Ax in FW vary 20–25 and in HW 15–18, Px in FW vary 14–20 and in HW 16–21. Anal loop 5–9 celled. Triangles 3–5 celled in FW, 4–5 celled in HW.

Measurements (in mm). HW 44.0–47.0; abdomen incl. appendages 46.0–52.0.

Differential Diagnosis. The male of P. crux is characterised by the combination of the disjoined cross pattern on S2 and paddle-shaped cerci, of which the paddle expands just before the mid-point of the cerci, and pale face. Female of P. crux is characterised by the combination of pale face, disjoined cross on S2 and pale amber wing bases.

Planaeschna cucphuongensis and P. chiengmaiensis (known from Thailand and China) are similar to P. crux. In addition to shorter paddles to the cerci, expanding just beyond the middle of the cerci (Fig. 11F), these two species lack green spots on the antealar sinus (Fig. 11J) and have dark brown wing bases, which is especially prominent in the females. The pattern on S2 is also distinctively different, although similar in general pattern (Figs 11H–I, 12E). The other species of the tamdaoensis -group have bright yellow and black facial patterns and are easily separated.

Ecology. This species was found at two geographically separated areas, but both at altitudes of around 1000 m asl. In Tu Le, Yen Bai Province, it was found along both smaller and larger streams traversing the national road, where they would hang up in the shade on particularly hot days or hawk at dusk. Fresh specimens were observed already in May and fully mature (=greenish) males in June. In Pia Oac NP fresh males were seen in September and fully mature males in October. There they were found hawking at dusk in small clearings in the forest near small streams. The difference in period of emergence is striking, but also observed between different populations of other species, like P. tamdaoensis and P. cucphuongensis.

Distribution. Endemic to Vietnam (Yen Bai Prov. and Cao Bang Prov.).

Note. The occurrence of this species at two separated locations in northern Vietnam suggests it may be commoner. It might be expected in southern China, for instance along the border with Cao Bang Province.