Ranatra gracilis Dallas, 1850

Polhemus, Dan A. & Polhemus, John T., 2013, Guide To The Aquatic Heteroptera Of Singapore And Peninsular Malaysia. X. Infraorder Nepomorpha-Famlies Belostomatidae And Nepidae, Raffles Bulletin of Zoology 61 (1), pp. 25-45 : 34

Ranatra gracilis Dallas, 1850

( Figs. 11, 12 )

Ranatra gracilis Dallas, 1850: 10

Material examined. — MALAYSIA, Selangor: 1 male, Kuala Lumpur, 1950, coll. Army Scrub Typhus Unit ( USNM) .

Extralimital material examined. — THAILAND, Chiang Mai Prov.: 4 males, 3 females, Fang Dist., Huay Hia Creek, Fang Horticultural Station , 500 m ., 15 Nov.1985, CL 2198, coll. D. A. & J. T. Polhemus ( JTPC) ; 1 male, Chiangdao , 450 m ., 5–11 Apr.1958, coll. unk. ( BPBM) . VIETNAM, Lai Chau Prov.: 2 males, small tributary streams to Lai River at Lai Châu, 230 m ., 22°02'35"N, 103°10'03"E, water temp. 23°C., 10 Apr.2000, 1600–1800 hours., J. T. Polhemus & P. Nguyen ( JTPC) . LAOS, Khammouane Prov.: 1 male, Phon Tiou , 11 Jun.1965, coll. N. Wilson ( BPBM) . Vientiane Prov.: 1 male, Van Heue [Ban Van Heue], 16 Mar.1966 ( BPBM) .

Diagnosis. — Male body length 28–29 mm, length of respiratory siphon 10–11 mm; female body length 29–30 mm, length of respiratory siphon 8–9 mm. Colouration, including legs, uniformly brown. Head with frons strongly tuberculate between the eyes. Ventral prothorax with a very shallow longitudinal sulcus, lateral margins of this sulcus weakly raised posteriorly, a prominent medial longitudinal carina present along entire length. Fore femur with single moderately small tooth near midpoint of the margin adjacent to the infolded tibia; middle and hind femora subequal in length; hind femur reaching to near tip of wing membrane in both sexes. Male paramere with a broad, curving incision subapically, separating a distal hook from a large, rounded subapical lobe with small tubercle, apex of distal hook well separated from subapical lobe and not contacting it ( Figs. 11, 12 ).

Distribution. — Originally described from Bhutan ( Dallas, 1850), with subsequent records from India (Assam), Thailand, and Peninsular Malaysia ( Lansbury, 1972). We provide the first records herein for Laos and Vietnam.

Discussion. — Ranatra gracilis is superficially similar in size and general external appearance to R. parmata , but may be separated by its slightly smaller size, better developed ventral prothoracic keel, and the shape of the male paramere apex ( Figs. 11, 12 ), which is armed with blade-like setae. This species is rare in collections, and is recorded from Peninsular Malaysia on the basis of only a single specimen, which was listed by Lansbury (1972) and also re-examined in the course of the current study.

Figures

Figs. 11–18. Ranatra species, male left parameres, outer view with detail of distal hook. 11, 12, R. gracilis, specimen from Laos, Vientiane Prov. 13, 14, R. parmata, specimen from Indonesia, Sumbawa (CL 2172). 15, 16, R. spinifrons, specimen from Malaysia, Selangor. 17, 18, R. varipes, specimen from Laos, Khammouane Prov.