Pseudagrion obscurum Lieftinck, 1936

Pseudagrion obscurum Lieftinck, 1936 stat. nov.

Figures: 59–60 (syntype ♂, envelope); 89a, b (head ♂); 106 (pterothorax ♂); 123a, b (abdomen ♂); 140a–c (caudal appendages ♂).

Pseudagrion pilidorsum obscurum View in CoL : Lieftinck (1936): 128, 131–132, Fig. 12b (key; description ♂ ♀; ♂ appendages; Nias & probably Simalur).

Name-bearing type specimens examined (2♂♂)

2♂♂ syntypes, 10.ix.1931, Amadraja, Nias Island , Indonesia, J.C. v. d. M. Mohr leg., RMNH, JvT no. 2839. Lieftinck (1971: 103) designated a lectotype male, but there are two males in the respective envelope (Figs

59–60). This lectotype designation is not valid because he has not explicitly designated a single specimen (ICZN

74.5). We do not consider it necessary to designate a lectotype, thus we propose to keep them as syntypes.

Other specimens examined (2♂♂, 1♀)

Indonesia, Nias Island: 2♂♂, 1♀, 21.iv.–2.v.1972, surroundings of Hilisimaetanoe, 200 m a.s.l., Roesler & Küppers leg., ZFMK, no. 2009/1142.1–1142.3 .

Characterization of male

Head ( Fig. 89a, b): Labrum, clypeus, antefrons and postfrons yellow-orange; postclypeus with two elongated black spots, and a black centre along posterior edge; centre of frons may have a small darkish spot; in one specimen the postclypeus is completely black ( Fig. 89b); yellow-orange colour of the postfrons is separated from black and red colour of the vertex at level of anterior margin of lateral ocelli; a black spot at posterior margin of median ocellus; a small reddish spot is situated in centre of vertex around level of posterior margin of lateral ocelli; occipital bar reddish; postocular spots washed-out dark reddish, comparatively small due to obscurely blackish margins; broadly surrounded by black; rear of head black, but may be yellow along the eye margins; base of antennae yellow, scape of antennae anteriorly yellow, but posteriorly black, following segments brownish.

Thorax ( Figs 59, 106): Anterior lobe of pronotum yellow, this colour expanding in centre towards middle lobe; margins of anterior lobe black; middle pronotal lobe black, with a centrally divided red patch in the middle, and on either side a red patch dorsolaterally; propleuron black above, yellowish below and to rear; posterior lobe yellowreddish, with its margins black; apical edge of posterior lobe convex. Pterothorax red; middorsal carina black; dorsum obscurely blackish, almost reaching to humeral suture; humeral suture with an elongated black patch at its posterior quarter, one male has also the anterior humeral suture thin black; interpleural suture with a black stripe at posterior quarter, and a black spot anteriorly; a black patch at posterior quarter of metapleural suture; a large black marking covering at least superior two-thirds of the mesinfraepisternum; venter pale, may be covered with whitish pruinosity. Legs pale, with outside of the femora obscurely blackish; tibiae blackish along spines; spines black.

Abdomen ( Figs 59, 123a, b): S1–2 dorsally black, laterally red; S3–8 dorsally black, laterally and each basal annulus yellow-orange; S9 red, with its posterior third to half black; S10 dorsally with black “x”-like marking, variable in shape; laterally red.

Caudal appendages ( Figs 140a–c): Cercus in lateral view darkish, shorter than S10, inferior lobe appears very slightly shorter than superior lobe; in lateral view cercus subrectangular with a shallow inter-lobe notch situated low on the apex; in dorsal view the terminus of the superior lobe of the cercus curved inwards; a small interior projection is situated around the centre of cercus; a small sharp-edged bulge-like interior projection before half-length on the inferior lobe of the cercus, visible in dorsal and dorsolateral views; paraproct pale brownish-ochre, around half as long as cercus; in lateral view subtriangular and tapered with rounded apex; in dorsal view broadly rounded, concave bowl-like; bearing a small black tooth at medial edge.

Characterization of female

Head: With dark markings as in male, but primary colour orange-ochre.

Thorax: Pronotum markings as in male, but primary colour yellow-orange; posterior lobe of pronotum with two black horns directed towards head, almost reaching the centre of the middle lobe. Pterothorax entirely reddish; humeral suture with an elongated black patch at posterior quarter; black markings at interpleural and metapleural suture narrow.

Abdomen: S1–10 dorsally black, laterally pale yellow-ochre; S9 pale yellow-ochre laterally, this expanded dorsally in centre; S10 with pale yellowish-ochre middorsal marking. Cercus blackish; paraproct brownish, in lateral view rounded; ovipositor pale yellowish-ochre, not reaching posterior margin of S10; two brownish styles reaching to beyond S10; inferior edge of ovipositor bearing several very small teeth.

Wings of both sexes with 12.5–14.5 px in forewing, and 11.5–13 px in hindwing.

Measurements of both sexes (mm): Total length (with appendages) 37.8–44.3; abdomen length (without appendages) 32.0–36.0; hindwing 21.8–24.5; forewing 22.9–27.5; Pt in forewing 0.8–1.0; male cercus 0.5–0.6.

Remarks

The single female has an entirely reddish pterothorax and lacks the name-giving obscurely blackish dorsum, which is present in all four males examined. It is not clear if this obscuring is just due to older age in the males or gender-related.

Diagnosis

Pseudagrion obscurum belongs to the group of endemic taxa of the island chain west of Sumatra. Due to scarcity of material we cannot give information on how to separate the females, but the males are separated from most congeners occurring on adjacent islands by having S1–2 dorsally black ( Figs 59, 123a, b). However this character is shared by P. igneum ( Figs 121a, b) and P. simalurum ( Figs 124a, b)—both are very similar to P. obscurum also in the colour of the head ( Figs 87, 89a, b, 90), and the morphology of the male cercus ( Figs 138a–c, 140a–c, 141a–c). We summarise a combination of characters for separating these three species in table 2.

Distribution

This species is apparently endemic to Nias Island ( Fig. 2).