Cercotmetus compositus Montandon, 1903

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 : 31-32

Cercotmetus compositus Montandon, 1903

( Fig. 5 )

Cercotmetus compositus Montandon, 1903: 109

Material examined. — MALAYSIA, Terengganu: 1 male, 1 female, N. of Rantau Abang, swamp at Km. 56 on road from Kuala Terengganu to Kuantan , 18 Mar.1992, coll. P. Ng, LHK 177 ( ZRC) ; 4 females, N. of Ayer Puteh, about 121 km. on road from Kuantan to Kuala Terengganu , 19 Mar.1992, coll. H. K. Lua, LHK121 ( ZRC) ; 4 males, 3 females, Rantau Abang , 15 May 1995, coll. H. H. Tan, THH9518 ( ZRC) . Johor: 2 males, 2 females, murky water tributary of Sungai Kahang , 10 Mar.1998, coll. H. H. Tan et al., THH9814 ( ZRC) ; 1 male, 1 female, swamp forest stream 61 km. N. of Johor Bharu on Mersing Road , 16 Oct.1986, CL 2220. coll. D. A. & J. T. Polhemus ( JTPC) ; 1 female, swamp forest stream 12 km. N. of Labis, nr. Ayer Panas , 22 Aug.1985, CL 2087, coll. D. A. & J. T. Polhemus ( JTPC) .

Extralimital material examined. — INDONESIA, 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) . Jambi Prov.: 1 female, Sumatra, Sungai Bakong, trib. to Danau Arang Arang , swamp forest, 1°37'31"S, 103°47'21"E, 25 Jul.1997, THH9743, coll. H. H. Tan ( ZRC) ; 2 females, Sungai Sentang, 12 km. SE of Jambi, nr. Desa Sukajaya , 27 Jul.1997, THH9744, coll. H. H. Tan ( ZRC) ; 2 males, 5 females, Sumatra, Sungai Alai , 21 Jun.1995, JMB9511, coll. unk. ( ZRC) . VIETNAM, Quang Tri Prov.: 1 male, 1 female, 1 mi. N. of Quang Tri, from stream, vigorous sweeping in vegetation, 15 Jun.1970, coll. A. R. Gillogly ( JTPC) .

Diagnosis. — Male body length 48–53 mm, length of respiratory siphon 13–16 mm; female body length 50–60 mm, length of respiratory siphon 14–16 mm. Head with interocular space usually less than the width of an eye, tuberculate between eyes. Mesosternum not carinate, depressed anterior of the middle coxae. Fore femur with single large tooth at mid-distance along the margin adjacent to the infolded tibia; middle femur about one-third longer than prothorax. Male paramere deeply bifid apically, this incision separating a slender, sinuate distal process from a more basal angulate process ( Fig. 5 ). Female with operculum narrow and sharply carinate, not extending beyond posterior apices of flanking ventral laterotergites.

Distribution. — Originally described from Indochina (composite series from Laos and Thailand) ( Montandon, 1903) and subsequently reported from Vietnam and Sumatra ( Lansbury, 1973). The Peninsular Malaysian material reported below fills a gap in the previously documented distribution, and represents the first definitive set of published records for this area, although it is possible that the Peninsular Malaysian records of Cercotmetus pilipes Dallas provided in Fernando & Cheng (1974) are also referable to this species. Despite occurring on both Sumatra and in Peninsular Malaysia, this species has not been recorded from intervening Singapore, although suitable habitats are present here.

Discussion. — This is the largest species of Cercotmetus occurring in Peninsular Malaysia, with male body lengths reaching up to 53 mm, and females up to 60 mm. It is similar to C. asiaticus in having a tuberculate vertex and a middle femur longer than the prothorax, but differs in lacking a metasternal keel, having a differently shaped male paramere (compare Figs. 5, 6 ), and possessing a short female operculum that does not extend posteriorly beyond the flanking abdominal ventral laterotergites. Additional characters separating this species from C. asiaticus include the generally dark colouration (versus yellowish brown in C. asiaticus ), and the prominent brushes of long hairs ventrally at the apices of both the middle and hind femora. Like C. brevipes , this is an uncommonly collected species that seems to be patchy in its distribution.

Figures

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).