Pseudagrion enganoense Lieftinck, 1948

Pseudagrion enganoense Lieftinck, 1948 stat. nov.

Figures: 31–32 (lectotype ♂, envelope); 85 (head ♂); 102 (pterothorax ♂); 119a, b (abdomen ♂); 136a–c (caudal appendages ♂).

Pseudagrion pilidorsum enganoense View in CoL : Lieftinck (1948): 290 –291, Fig. 6 (description ♂ ♀; Engano).

Name-bearing type specimen examined (1♂)

♂ lectotype, 30.v.1936, Buahbuah , Enggano Island, RMNH, JvT no. 2816 ( Figs 31–32) .

Lectotype designation by Lieftinck (1971: 86). Lieftinck (1948) spelled the island “Engano”, that’s why the scientific name is written with a single “g”. However, today the island is spelled “Enggano”.

Other specimens examined (2♂♂)

Indonesia, Enggano Island: 2♂♂, 30.v.1936, Buahbuah, RMNH, no. 1658925, 1658926 .

Characterization of male

Head ( Figs 31, 85): Labrum, clypeus, antefrons and postfrons yellow; colour of postfrons distinctly separated from vertex around the level of lateral ocelli; vertex red, with a small black spot posterior of median ocellus, and large black patches each along interior and posterior margin of lateral ocelli; postocular spots red, separated by black line from postfrons and vertex; rear of head black, but yellow-orange along the eye margins; base and scape of antennae yellow, following segments brownish.

Thorax ( Figs 31, 102): Anterior lobe of pronotum yellowish, expanding in centre spot-like towards middle lobe, anterior margin black; middle pronotal lobe black, with a centrally divided yellowish patch in the middle, and on each side a yellowish spot dorsolaterally; propleuron black above, yellowish below and to rear; posterior lobe of pronotum yellowish; apical edge of posterior lobe convex. Pterothorax red, with thin black middorsal carina; humeral suture and metapleural suture with black streaks at posterior quarter; interpleural suture with a thin black line; ventrally pale, may be covered with whitish pruinosity. Legs pale orange-reddish; femora with blackish stripe outside, narrowing proximally; tibiae blackish along spines; spines black.

Abdomen ( Figs 31, 119a, b): S1 red, S2 red with its posterior margin black; S3–8 dorsally black, laterally pale orange-yellow; S9 black with anterior third to half red; S10 black, ventrally pale.

Caudal appendages ( Figs 136a–c): Cercus laterally obscure reddish; slightly shorter than S10, inferior lobe slightly longer than superior; in lateral view subrectangular, apex with inter-lobe notch deep and almost central; in dorsal view cercus appearing narrow, with terminus of superior lobe slightly turned in, bifurcated interiorly (visible in dorsolateral view); a small almost centrally-placed interior tooth-like projection on the inferior lobe of the cercus; paraproct pale ochre; around half as long as cercus; in lateral view subtriangular and tapered with rounded apex; in dorsal view broadly rounded, concave bowl-like, with blackish tubercular medial edge.

Measurements (mm): Total length (with appendages) 42.3–44.5; abdomen length (without appendages) 35.7– 36.7; hindwing 23.7–24.3; forewing 25.0–26.0; Pt in forewing 0.7–1.0; male cercus 0.5–0.6.

Characterization of female [not examined, characterization adopted from Lieftinck (1948)]

Head: As in male but ochraceous instead of yellow.

Thorax: Pterothorax as in male but dorsally honey-yellowish, fading to cinnamon-buff laterally; markings at humeral and metapleural suture rusty.

Abdomen: As in male but with S1–2 orange; S9 with a large yellow spot laterally; ovipositor yellowish.

Wings of both sexes with 14.5–17 px in forewing, and 13–16 px in hindwing [adopted from Lieftinck (1948), and own data].

Diagnosis

Pseudagrion enganoense belongs to the group of endemic taxa of the island chain west of Sumatra. The morphology of the male cercus of P. enganoense is distinct: its inferior lobe is slightly longer than superior one ( Figs 136a, b), and in dorsolateral view the inner margin of superior lobe of cercus lacks an inward projection proximal of its bifurcated terminus ( Fig. 136c). Additionally both sexes of P. enganoense can be separated from congeners on adjacent islands by having S1–2 red in the male ( Figs 31, 119a, b), orange in the female. This character is shared with P. declaratum , P. deflexum , and P. nigrihumerale ( Figs 117a, b, 118a, b, 122a, b). However P. nigrihumerale can also be separated by its broadly black antehumeral stripe ( Fig. 105), while P. declaratum as well as P. deflexum have much larger red postocular spots than P. enganoense , not bordered by black except for a very small blackish line on vertex ( Figs 26, 29, 31, 83, 84, 85, 155, 157).

Distribution

Endemic to Enggano ( Fig. 2).