Leptogomphus tioman, Choong, Chee Yen, 2016

Choong, Chee Yen, 2016, Leptogomphus tioman sp. nov. (Odonata: Anisoptera: Gomphidea) from Tioman Island, Peninsular Malaysia, Zootaxa 4171 (2), pp. 382-388 : 382-385

Leptogomphus tioman sp. nov.

Material. Holotype: Ƌ (TIO3_GOM1), Peninsular Malaysia, Pahang, Tioman Island, Mukut, a small rocky stream at the foothill of Si-Mukut , 18 v 2014, CYC leg . Paratypes: 2 Ƌ (TIO4_GOM2,3), Sg. Raya, Tioman Island, Mukut, a small rocky stream at the back of Mukut Village , 18 iv 2016, CYC leg; m (TIO4_GOM1), upstream of Sg. Asah, Tioman Island , 17 iv 2016, CYC leg; 2Ƌ (TIO4_GOM4,5), Sg. Asah, near Asah Waterfall, Tioman Island , 19 iv 2016, CYC leg. Holotype to be deposited in Institut Biodiversiti (IBD) Lanchang, Department of Wildlife and National Parks ( DWNP) Peninsular Malaysia , paratypes in collections of Centre for Insect Systematics (Universiti Kebangsaan Malaysia) (TIO4_GOM1,2,5) and the IBD (TIO4_GOM3,4).

Etymology. The specific name is a noun in apposition and named after Tioman Island, the type locality.

Description of holotype male. A medium-sized dragonfly with greenish yellow markings ( Fig. 1 ). Head: Vertex mainly black, but brown behind tubercles posterior to lateral ocelli; occiput also brown with brown setae. Frons distinctly swollen, mostly greenish yellow. Labrum black with a pair of broad greenish-yellow stripes next to clypeus. Clypeus black with a paired oval depression on postclypeus. Mandibles totally black with greenish-yellow marking at base. Labium greenish yellow.

Thorax: Prothorax with anterior lobe mainly greenish yellow ( Fig. 2 ); middle lobe with deep median depression anteriorly, a pair of middorsal yellow spots and greenish yellow in lateral edges; posterior lobe dark brown. Synthorax black with greenish-yellow markings; dorsal thoracic stripes broadly connected to sections of mesothoracic collar, which is interrupted medially ( Fig. 2 ); yellow marking on mesepimeron and pale yellow marking on metepisternum; metepimeron largely yellow with thick black anterior margin ( Fig. 3 ). Wings: Forewing with 16 Ax, 15 Px; hindwing with 13 Ax and 16 Px. Pterostigma dark brown, 3.0 mm. Arculus about 1/3 distance between second and third Ax. Cu crossing proximal to first Ax. Triangle, subtriangle and supratriangle all without crossveins. Legs: stoutly built. All femora with short spines on inner side; all tibiae with two rows of long spines on inner side.

Abdomen: Nearly black with narrow yellow middorsal stripe visible on S1–2. S1 side yellow, S2 with a pair of ventral yellow markings and S3 anterolateral side also yellow. Auricules with yellow marking hardly developed. Abdomen gradually expended from tip of S7, reaching the widest point at tip of S8, then narrowing gradually to tip of S10. Dorsum S10 covered with small denticles ( Figs. 4–6 ). Anal appendages: Cerci black ( Figs. 4–6 ), thick at base and curved slightly inward at about apical 2/3, turned slightly upward at tip; tip of cerci rather sharp in dorsal and lateral views. Lower edge of cercus produced outward and sharply angled inward for apical 1/3; outer margin of angle bearing strong serration ( Figs. 4 , 8 ). Small conical, subapical, ventral process on each cercus, visible in oblique dorsal view ( Figs. 6 , 13 ). In lateral view ( Figs. 5 , 11 ), cercus robust, broad, straight-sided, tapered upwards to a point from apical 2/3; outer surface of cercus covered with small denticles apically. In ventral view, epiproct black, making a wide V-shape before diverging outward to tips; in lateral view bending evenly upward with a dorsal hook at tip. Genitalia ( Figs. 7 , 14 ): Anterior hamule with broad base and pronounced shoulder, tapering posteriorly to a thin layer. Posterior hamule broad throughout, with a pronounced curve point at apical part. Vesica spermalis with rounded posterior lobe on basal segment and two diverging flagella on distal segment.

Measurements of male: Abdomen (incl. appendages) 40.0 mm. Hindwing 31.5 mm.

Female: unknown.

Diagnosis. A greenish-yellow marked Leptogomphus , readily distinguished from all known regional species except L. risi by its thoracic marking, and from all species by the unique structure of its cerci. The tips of cerci in dorsal view are sharp in L. tioman but round in L. risi . The tips of the epiproct are closer together in L. tioman than L. risi . Compared to L. risi , the outer margins of the epiproct in L. tioman appear sinuous rather than convex.

Habitat. Adults are found on lowland small streams with a sand and gravel substrate in primary as well as secondary forests. The water is clean and flow is slow to moderate.

Behavior. Male adults were spotted at noon on sunny days. The adults frequently perched in sunspots on leaves next to the water ( Fig. 17 ). When alarmed, they flew into the canopy perching on leaves, returning to their former perch after a short interval (roughly 5 minutes).

Figures

FIGURE 1. Leptogomphus tioman, holotype, lateral view, scale bar = 20.0 mm.

FIGURE 17. Leptogomphus tioman male, Sg. Raya, Tioman Island, Peninsular Malaysia, 18 April 2016.

FIGURES 2 – 7. Leptogomphus tioman, holotype: (2) thorax, dorsal view in live; (3) thorax, lateral view; (4) anal appendages, dorsal view; (5) anal appendages, lateral view; (6) anal appendages, oblique dorsal view; (7) accessary genitalia, lateral view.

FIGURES 8 – 14. Anal appendages: (8) L. tioman holotype, dorsal view; (9) L. risi, Malaysia, dorsal view, redrawn from Asahina (1986); (10) L. risi, Thailand, dorsal view, redrawn from Asahina (1986); (11) L. tioman holotype, lateral view; (12) L. risi, Thailand, latral view, redrawn from Asahina (1986); (13) L. tioman holotype, oblique dorsal view; (14) L. risi, Malaysia, oblique dorsal view, redrawn from Asahina (1986).