Cercotmetus, Amyot & 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 : 28

Genus CERCOTMETUS Amyot & Serville, 1843

( Figs. 3–7 )

Discussion. — The genus Cercotmetus contains 10 species (exclusive of subspecies) occurring in Asia and Australia. The taxonomy was competently revised by Lansbury (1973), with only C. minutus Keffer & J. Polhemus from Laos having been subsequently described. Unlike other nepids, Cercotmetus species occur along the margins of flowing streams, where they may sometimes be observed swimming near shore. The individual species are solitary in their habits, and not generally collected in large numbers. As such, the geographic ranges of the constituent taxa are still incompletely understood, and the records provided below serve to fill in a number of distributional gaps.

Key morphological apomorphies defining Cercotmetus as provided by Lansbury (1973) include the outer margin of the eyes sloping downward and obscuring the ventral margin of the head, the length of the fore femur shorter than the prothorax, the middle and hind tibiae with fringes of long swimming hairs, and the phallotheca housed in a membranous anterior diverticulum rather than within the sclerotized genital capsule. The eggs of Cercotmetus bear slender, elongate respiratory horns that are much longer than the egg itself, being in some cases up to 10 mm in length (see Fig. 1 in Lansbury, 1973). Similar respiratory horns are also found in Ranatra , but are shorter that those of Cercotmetus , at least in all tropical Asian Ranatra species for which this character state is known.

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.

Fig. 1. Lethocerus indicus (Lepeletier & Serville), male, specimen from Laos, Vientiane Prov.