Cercotmetus asiaticus Amyot et Serville, 1843

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 : 29-30

Cercotmetus asiaticus Amyot et Serville, 1843

( Figs. 3 , 6 )

Cercotmetus asiaticus Amyot & Serville, 1843: 441

Material examined. — SINGAPORE: 2 males, Selatar Reservoir, Park Stream , 10 May 1991, coll. C. M. Yang et al. ( ZRC) ; 3 males, stream at end of Rifle Range Road , 27 May 1993, coll. C. M. Yang et al. ( ZRC) ; 2 males, Nee Soon swamp forest, 14 Apr.1990, coll. P. K. L. Ng ( ZRC) . MALAYSIA, Johor: 6 males, 3 females, Muar – Labis road, Sungai Tui , 26 Jul.1992, coll. K. Lim et al. ( ZRC) ; 10 males, 2 females, 4 immatures, Sungai Temantang , 24 Feb.1995, coll. H. K. Lua et al. ( ZRC) ; 1 male, 1 female, Layang Layang , stream 2, clear water, sandy bottom, 6 Feb.1991, coll. ZRC staff ( ZRC) ; 1 male, Layang Layang , stream 3, muddy pond with vegetation, 6 Feb.1991, coll. ZRC staff ( ZRC) ; 2 males, stream nr. Pulai Reservoir , 23 May 1991, coll. C. M. Yang & K. L. Yeo ( ZRC) ; 1 male, Kota Tinggi, eastern foothills of Gunung Pantai ( Track 266), 22 Oct.1991, coll. P. K. L. Ng et al. ( ZRC) ; 1 male, stream in rubber estate at foot of Mt. Ophir , close to Muar Reservoir, Tankak, 4 Nov. Perlis : 2 males, Sintok – Padang, Senai Rd. , 19 Feb.1997, coll. H. K. Lua, LHK0330 ( ZRC) .

Extralimital material examined. — MALAYSIA, Sarawak: 1 male, 1 female, Borneo, Sungai Stok Muda , 6 Sep.1995, coll. H. H, Tan ( ZRC) ; 2 males, 1 female, Borneo, outside Gua Kapo , 7 Sep.1995, coll. H. H. Tan, THH9567 ( ZRC) ; 2 males, 2 immatures, Borneo, Kapit Dist., Sungai Ulu Selirik, 20 mi. upsteam of Rejang , 2°00'01"N, 112°57'24"E, 2 Mar.1998, THH9808, coll. H. H. Tan & R. Kerle ( ZRC) ; 1 male, 1 female, Borneo, stream draining from Gunung Gading, 3 km. before turnoff to Cape Pelandok, nr. Lundu , 1°44'18"N, 112°52'01"E, 2 Sep.1996, THH9692, coll. H. H. Tan ( ZRC) . Sabah: 1 male, 1 female, Borneo, Danum Valley, Sungai Bole Kecil trib., 4°57'33"N, 117°51'34"E, 2 Oct.1996, THH96122, coll. H. H. Tan ( ZRC) ; 1 female, stream 5 km. S. of Poring Hot Springs , 2 Aug.1985, CL 2024, coll. D. A. & J. T. Polhemus ( JTPC) . INDONESIA, Jambi Prov.: 2 females, Sumatra, Sungai Sentang, 12 km. SE of Jambi, nr. Desa Sukajaya , 27 Jul.1997, THH9744, coll. H. H,. Tan ( ZRC) . Palembang Prov.: 1 male, 1 female, Sumatra, Sungai Simpang, small trib. entering Sungai Niru from E. immediately upriver from Muaranira , 22 Feb.1995, coll. M. Kottelat ( ZRC) . Riau Islands Prov. : 3 males, Batam Is., 29 Jan.1991, coll. P. K. L. Ng ( ZRC) ; 5 males, 1 female, Bintan Is., 47 km. to Tanjung Pinang, 1°06'38.1"N, 104°29'18.0"E, 27 Apr.1994, HH008, coll. unk. ( ZRC) . Bangka-Belitung Prov.: 1 male, 2 females, Bangka Is., 5.5 km. N. of Payung , secondary forest, blackwater, pH 4.9, 5 Mar.1993, coll. M. Kottelat ( ZRC) . Kalimantan Barat Prov.: 1 male, Gunung Palung Nat. Park, Cabang Panti Research Station , 100– 400 m., primary rain forest, 1°15'S, 110°05'E, 15 Jun.–1 Jul.1991, coll. Darling, Rosichon & Sutrisno ( JTPC) . BRUNEI, Belait Dist.: 1 male, 1 female, Borneo, Labi, Rampayoh, Sungai Mendaram and Mendaram Falls , 11 Oct.2001, coll. H. H. Tan and K. K. P. Lim ( ZRC) . Temburong Dist.: 1 male, Borneo, Belalong Basin, Sungai Enkabang , 5 Oct.2001, coll. H. H. Tan & K. K. P. Lim ( ZRC) . CHINA, Yunnan: 2 males, Xishuangbanna, 67 km. from Mengla , rocky stream, 1 Jun.2002, coll. C. M. Yang & P. Chew, YCM0311 ( ZRC) ; 1 male, Xishuangbanna, Manchang stream, 63 km. from Jinghong to Menglun , rocky stream, 30 May 2002, coll. C. M. Yang & P. Chew, YCM0300 ( ZRC) . CAMBODIA: 1 female, between Phnom Penh and Kampong Som, Trueck Chai River , 24 May 1999, coll. H. H. Tan & H. N. Ng, THH9924 ( ZRC) . BURMA, Mandalay Division: Gelaung River at Pwe Kauk Falls , 8 km. E. of Maymyo , 1005 m., 22°03.52'N, 96°31.96'E, 19 Oct.1998, CL 4012, coll. D. A. & J. T. Polhemus ( JTPC) .

Diagnosis. — Male body length 46–50 mm, length of respiratory siphon 10–12 mm; female body length 49–53 mm, length of respiratory siphon 11–16 mm. Head with interocular space greater than the width of an eye, tuberculate between eyes. Mesosternum bearing a prominent keel. Fore femur with single relatively small tooth at mid-distance along the margin adjacent to the infolded tibia; middle femur much longer than prothorax. Male paramere deeply and narrowly bifid apically, this incision separating a pair (1+1) of sharply angulate processes ( Fig. 6 ). Female with operculum very long, extending posteriorly well beyond posterior apices of flanking ventral laterotergites.

Distribution. — Originally described from Java, and subsequently recorded from Sumatra, Borneo, Peninsular Malaysia (Johor, Perak, Pahang, Malacca), Vietnam, Thailand, and China ( Lansbury, 1973; Fernando & Cheng 1974; Chen et al., 2004). The material listed below includes the first published records for Singapore and the Peninsular Malaysian states of Selangor, Negeri Sembilan, Terengganu and Perlis.

Discussion. — The most commonly encountered Cercotmetus in Singapore and Peninsular Malaysia, C. asiaticus may be easily recognised by its tuberculate vertex, longitudinally carinate mesosternum, distinctive male paramere ( Fig. 6 ), and very elongate female operculum that extends posteriorly well beyond the flanking ventral laterotergites. It is occasionally encountered syntopically with the smaller and stouter C. brevipes (compare body shapes in Figs. 3 , 7 ).

Montandon (1909) described the variety C. asiaticus var. longicollis , based on specimens with a more elongate and parallel-sided prothorax in comparison to the typical form. We suspect that this morphological variation may be linked to degree of wing development, and have not treated this form as a separate subspecies herein. Lansbury (1973) could not locate the specimens upon which Montandon based this name, but did list two others, one from Borneo, and another from Malacca in Peninsular Malaysia. Therefore this form is known to occur in the region under study.

Figures

Fig. 3. Cercotmetus asiaticus Amyot & Serville, female, specimen from Thailand, Chiang Mai Prov.

Figs. 4–6. Cercotmetus species, male parameres. 4, C. brevipes, specimen fromVietnam,Quang Tri Prov.5, C. compositus, specimen from Malaysia, Johor (CL 2220). 6, C. asiaticus, specimen from Vietnam, Gia Lai Prov. (CL 4286).

Fig. 7. Cercotmetus brevipes Montandon, female, specimen from Thailand, Chiang Mai Prov.