Drepanosticta sbong, Dow, 2010

Dow, Rory A., 2010, Two new Platystictidae (Odonata: Zygoptera) from Sarawak, Malaysian Borneo, Zootaxa 2412, pp. 63-68 : 63-66

Drepanosticta sbong sp. nov.

( Figs. 1–7)

Material. Holotype: ♂ (SAR07_8_PST30), Malaysia, Sarawak, Kapit Division, vicinity of Kapit town , Sg. Sbong (tributary of the Baleh river) in disturbed forest on native customary rights land, N 2º 0.280’ E 113º 6.606’, ca 50 m, 11–II–2008, leg. G. T. Reels . Paratype: 1 ♀ (SAR07_8_PST31), data as holotype; the holotype male was attempting to form tandem with the female when captured . Holotype and paratype to be deposited in RMNH .

Etymology: Sbong, a noun in apposition. Named for the type locality, Sg. Sbong.

Description of holotype male. Head ( Fig. 1): Labium yellowish cream except end hooks of labial palps, which are brown. Labrum yellowish cream except centrally along free margin, where narrowly black. Anteclypeus yellowish cream, postclypeus shining black. Mandible bases largely yellowish cream above, dark brown along lower margin and beside genae. Genae dark brown. Frons and vertex bronzy black, occiput very dark brown, shiny. Vertex relatively broad; ratio of width of compound eye to width of vertex measured at level of lateral ocelli ca 2/3. Transverse occipital carina with lateral extremities angulated and quite prominent. A tuft of setae just above the carina, directly behind each lateral ocellus. Ocelli whitish, distance between lateral ocelli slightly greater than that between either lateral ocellus and median one. Antennae brown except for grey ring at top of scape.

Thorax: Prothorax with propleuron yellowish cream. Pronotum with anterior and median lobes yellowish cream, except around central pit of median lobe, where brownish. Each hemisphere of median lobe bearing a clump of setae dorsally. Posterior pronotal lobe brown, free margin simple, straight, laterally with a pair of hanging process, narrow and directed downwards and rearwards at ca 45 degrees to rear margin of propleuron ( Fig. 2). Synthorax: Mesepisternum entirely bronzy black, antealar triangles dark brown. Mesepimeron bronzy black. Metepisternum yellowish cream with a dark brown wedge above the metepleural suture and continued alongside the antealar carina. Metepimeron yellowish cream except narrowly centrally immediately below metepleural suture, where brownish. Venter of synthorax pale. Legs: each with coxa and trochanter yellowish cream, femur same at base, becoming greyish distally, dark around joint, as is the tibia, which is dirty cream with obscure brown markings below. Tarsi brown. Wings: 13 (left) or 14 (right) Px in Fw, 13 (left) or 12 (right) Px in Hw. Arculus distal to Ax2. Left Hw with 3 Ax. R 4 arising distal to subnodus, IR 3 joined to it by a short stalk. 1A entering wing margin just beyond level of Px 3 in Fw, just proximal to Px 4 in Hw. Pterostigma pale brown with a paler margin, approximately rectangular, covering slightly more than one underlying cell.

Abdomen: Largely brown. S1–2 brown above, yellowish cream laterally. S3–7 brown with a faint basal pale annulus, broadly interrupted dorsally, paler laterally along free margin of sternite, this becoming less clear on progressive segments. S8 dark brown above, yellowish laterally on lower third. S9–10 dark brown laterally, S9 with a pale blue longitudinal band dorsally, S10 almost entirely pale blue dorsally, rear of S9 and all of S10 depressed (possibly crushed, but see comments in the diagnosis) centrally. Caudal appendages ( Figs. 5–7): Cerci dark brown at base, becoming paler by the tips, slender, strongly down-turned at ca 2/3 length ( Fig. 5), tips slightly expanded, flattened. Paraprocts coloured similarly, directed upwards, in lateral view tips somewhat expanded and appearing rounded. Internally with a large triangular expansion near base, a smaller triangular expansion just before the tips, which are abruptly in turned and very slender, these features best seen in ventral view ( Fig. 7). Genital ligula partly visible, the terminal segment broad and the cleft between the arms concave, with 2–3 bristles on either side of the shaft.

Measurements (mm): Abdomen without caudal appendages 28.5, cerci ca 1, Hw 19.

Description of paratype female. As male except as noted. Head ( Fig. 3): Pale markings on labrum and anteclypeus blue, those on labrum slightly less extensive than in male. Mandible bases with only a small pale mark in upper 1/3.

Thorax: Prothorax with posterior pronotal lobe with lateral processes shorter than in male and directed slightly outwards ( Fig. 4). Wings: 13 Px in all wings. R 4 arising at (left) or very slightly proximal (right) to subnodus. 1A entering wing margin at around level of Px 3 in all wings.

Abdomen: S3–7 without pale basal annuli. S9 dark brown except for an obscurely pale area centrally laterally. S10 blue dorsally, very short. Ovipositor extending ca twice the length of S10 beyond S9, with gonapophyses brown, outer valve of S9 largely pale brownish cream with obscure darker markings, styles brown.

Measurements (mm): Abdomen without cerci or ovipositor 29, gonapophyses just less than 2, Hw 21.

Diagnosis. Easily separated from all described species known from Borneo except for D. crenitis Lieftinck , D. dentifera Kimmins , D. forficula Kimmins , D. monoceros Lieftinck and Protosticta versicolor Laidlaw by the combination of synthorax without antehumeral markings and terminal abdominal segments with pale markings. The male is separated from the above-mentioned species by the form of the caudal appendages and structure of the pronotal posterior lobe; the female by the form of the pronotal posterior lobe.

The relationships of this species to the other Bornean Platystictidae are not clear at present, but its closest ally may be D. forficula , to which it is very similar in size and colouration at least. Specimens of D. forficula and closely allied forms in my collection also have S9–10 noticeably narrower in lateral view than S8, and in some cases depressed dorsally, as in male D. sbongi .