Ranatra thai Lansbury, 1972

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 : 36-38

Ranatra thai Lansbury, 1972

( Figs. 10 , 21, 22 )

Ranatra longipes thai Lansbury, 1972: 334

Ranatra thai: Tran & D. Polhemus, 2012: 102

Material examined. — The following additional records are in addition to those listed in Tran & Polhemus (2012): MALAYSIA, Johor: 2 males, 3 males, Pontian, stream along road to Pekan Nanas, 15 Aug.1995, coll. H. K. Lua ( ZRC) ; 2 males, 1 female, Layang Layang stream 1, muddy water with vegetation on side, 6 Feb.1991, coll. NUS staff ( ZRC) . Perak: 1 male, near Sungai Bernam headwater works, 16 Jun. 19919, coll. H. K. Lua, LHK160 ( ZRC) .

Diagnosis. — Male body length 21–24 mm, length of respiratory siphon 18–24 mm; female body length 22–27 mm, length of respiratory siphon 18–24 mm. Colouration including legs medium brown. Head with vertex raised centrally ( Fig. 10 ), sometimes with a small nodular tubercle in males. Ventral prothorax with a prominent medial longitudinal setiferous carina present along entire length. Fore femur long and slender, with two teeth distal of midpoint on the margin adjacent to the infolded tibia, consisting of a moderate sized tooth on outer face and a smaller tooth on inner face (similar to Fig. 27 ); middle and hind tibiae subequal in length, both longer than both middle and hind femora; hind femora in both sexes when folded back along body slightly exceeding apex of operculum. Male paramere with a moderately broad and deep incision subapically, isolating a distal hook that is only weakly expanded distally and not weakly toothed; subapical lobe absent ( Figs. 21, 22 ).

Distribution. — Originally described from Thailand ( Lansbury, 1972) and subsequently recorded from Langkawi Island in the Peninsular Malaysian state of Kedah (Zettel & Tran, 2009). Additional records for the Peninsular Malaysian states of Terengganu, Selangor, Pahang, Malacca, and Johor, as well as from further localities in Vietnam, and Thailand, were provided by Tran & D. Polhemus (2012), and we provide new records from the Malaysian states of of Johor and Perak herein.

Discussion. — Lansbury (1972) described the subspecies Ranatra longipes thai based on specimens from various localities in Thailand. Tran & D. Polhemus (2012), following a fine-scale analysis of male paramere structure, elevated Lansbury’s subspecies to full species status. This is the most widespread and commonly encountered Ranatra species in Peninsular Malaysia north of Johor, but definitive separation from R. longipes requires measurement of leg segment ratios, or a genitalic dissection. In R. thai the distal hook of the male paramere lacks a small subapical tooth (compare Figs. 19, 20 to 21, 22), and the middle and hind femora are subequal in length, rather than the hind femur being distinctly longer than the middle femur as in R. longipes .

Figures

Figs. 9–10. Ranatra species, left lateral view of head.9, R. parmata, specimen from Indonesia, Sumbawa (CL 2172). 10, R. thai, specimen from Thailand, Chiang Mai Prov. (CL 2201).

Figs. 19–24. Ranatra species, male left parameres, outer view with detail of distal hook. 19, 20, R. longipes, specimen from Singapore, Nee Soon. 21, 22, R. thai, specimen from Thailand, Chiang Mai Prov. (CL 2201). 23, 24, R. rafflesi, specimen from Singapore, Selatar Reservoir.

Figs. 27–29. Ranatra species, forelegs. 27, R. longipes longipes, specimen from Singapore, Nee Soon.28, R. rafflesi, specimen from Singapore, Selatar Reservoir. 29, R. varipes, specimen from Laos, Khammouane Prov.