Guide To The Aquatic Heteroptera Of Singapore And Peninsular Malaysia. X. Infraorder Nepomorpha-Famlies Belostomatidae And Nepidae Author Polhemus, Dan A. Author Polhemus, John T. text Raffles Bulletin of Zoology 2013 2013-02-28 61 1 25 45 journal article 10.5281/zenodo.5351508 2345-7600 5351508 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.