Dineutus (Rhombodineutus) virescens Ochs, 1955

Polhemus, Dan A., 2011, New distributional records for Gyrinidae (Insecta: Coleoptera) on New Guinea and nearby islands, with a checklist of the New Guinea species, Zootaxa 2900, pp. 51-68 : 56-58

Dineutus (Rhombodineutus) virescens Ochs, 1955

Fig. 3

Dineutus (Rhombodineutus) virescens Ochs, 1955: 144 .

Material examined. INDONESIA, Papua Prov. [= former Irian Jaya Prov.]: 2 males, 2 females, upper Minajerwi River and swift tributary, approx. 1 km. E. of Mile 50 tank farm on Tembagapura Road, 500 m. [1650 ft.], 4°16'59"S, 137°01'34"E, water temp. 23° C. (river), 22° C. (trib.), 25° C. (side pools by river), 24 January 1997, 12:00–14:00 hrs., CL 7061, D. A. Polhemus ( USNM); 1 female, blackwater stream 2.4 km. S. of Mile 50 storage tank site on Tembagapura Road, 31.5 km. N. of Timika, 580 m. [1900 ft.], 4°17'56"S, 136°59'59"E, water temp. 25° C., 19 January 1997, 11:15–12:00 hrs., CL 7047, D. A. Polhemus ( USNM). PAPUA NEW GUINEA, Southern Highlands Prov.: 5 females, Kikori River basin, small rocky creek in disturbed forest, approx. 1.0 km. N. of Tubage, NE of Moro, 1000 m. [3280 ft.], water temp. 21° C., 14 March 1995, 14:30-15:00 hrs.; 22 March 1995, 13:00-13:30 hrs., CL 7022, [6°19'43"S, 143°17'30"E], D. A. Polhemus ( USNM); 3 males, 1 female, Kikori River basin, rocky stream entering Lake Kutubu nr. Inu, 800 m., water temp. of stream 24° C., of lake 30° C., 15 March 1995, 10:45-12:15 hrs., CL 7025, [6°21'45"S, 143°18'16"E], D. A. Polhemus ( USNM); 2 males, 2 females, Kikori River basin, Auwa Creek, nr. Kafka, NW of Kantobo, 520 m. [1705 ft.], 06°35'09"S, 143°30'21"E, water temp. 22° C., 9 March 1995, 10:30-14:00 hrs., CL 7013, D. A. Polhemus ( BPBM); 3 males, 3 females, Kikori River basin, Ofake Creek, trib. to Mubi River, 2 km. NW of Kantobo, 380 m. [1245 ft.], water temp. 23.5° C., 11 March 1995, 10:00-13:00 hrs., CL 7016, [6°43'00"S, 143°32'37"E], D. A. Polhemus ( BPBM); 2 males, 11 females, Kikori River basin, branch of upper Kara Creek (trib. to Digimu River), 5.5 km. S. of Moro oil camp, on road to Ridge camp, 900 m. [2850 ft.], water temp. 20° C., 12 March 1995, 13:40-16:30 hrs., CL 7017, [6°23'19"S, 143°13'08"E], D. A. Polhemus ( BPBM); 1 male, 8 females, Kikori River basin, branch of upper Kara Creek (trib. to Digimu River), 3.5 km. S. of Moro oil camp, on road to Ridge camp, 900 m. [2850 ft.], water temp. 20° C., 13 March 1995, 08:40- 11:30 hrs., CL 7018, [6°22'38"S, 143°13'06"E], D. A. Polhemus ( BPBM); 9 females, Kikori River basin, stream at Ludesa Mission, N. of Mt. Bosavi, 700 m. [2295 ft.], 06°27'57"S, 142°50'31"E, water temp. of stream 23° C., 20 March 1995, 12:30-14:30 hrs., CL 7019, D. A. Polhemus ( BPBM).

Discussion. The type series of this species came from the upper Lorentz River system, not far from the new Timika collections reported below, and this species has also been previously recorded from the Fly River system ( Brinck, 1983). New collections have now shown that the range of this species extends eastward through the southern New Guinea premontane foreland as far east as the Kikori River basin of Papua New Guinea ( Fig. 3 ), where it is commonly encountered across a wide range of elevations.

At Auwa Creek, near the village of Kafka in the Kikori system, Dineutus (Rhombodineutus) virescens was taken along the margins of a swift, clear, rocky stream heavily shaded by relatively undisturbed upland rain forest, running through karst terrain, with a water depth of 0.25–1.00 m., and a clean bed substrate of rough limestone cobbles. At a higher elevation in the Kikori system this same species was taken on a headwater branch of Kara Creek, 3.5 km. from the Chevron Niugini oil camp at Moro, on a small upland stream heavily shaded by tall Nothofagus forest. The stream was shallow and clear, with a moderate bed profile creating alternating riffles and flowing pools, and a bed substrate consisting of a complex mixture of cobbles, gravel, and fine sediment, with a few larger rocks intermixed. As demonstrated by the records presented, the species was also captured on many other rocky tributary streams in the Kikori Basin exhibiting similar physical characteristics to the examples cited above. Based on known collections, this species occupies the Arafura Foreland and Papuan Gulf Foreland areas of freshwater endemism (Areas 23 and 26 respectively) as defined by Polhemus & Allen (2007), and given this distribution should also be expected to occur in the intervening Trans-Fly Foreland area of endemism (Area 24).

This is the species listed as “ Dineutes (Rhombodineutus) sp.” in Tables 14, 18, 19, 20, 24, 26, and 30 in Polhemus (1995).

Dineutus (Rhombodineutus) helleri stueberi Ochs, 1955 Fig. 3

Dineutus (Rhombodineutus) helleri stueberi Ochs, 1955: 146 .

Material examined. INDONESIA, Papua Prov. [= former Irian Jaya Prov.]: 3 males, 6 females, Cyclops Mountains, rocky stream above Pos Tujuh, NW of Sentani, 260– 300 m. [850–1000 ft.], 2°32'26"S, 140°30'47"E, water temp. 22.5 °C., 18 September 2000, 14:00–16:30 hrs., CL 7145, D. A. Polhemus ( USNM).

Discussion. All records of this taxon have come from the Cyclops Mountains, an isolated massif on the northern central coast of New Guinea. The nominate subspecies, Dineutus (Rhombodineutus) helleri helleri , occurs in the Bougainville and Torricelli Mountains immediately to the east along the north coast of New Guinea ( Brinck, 1983).

At Pos Tujuh, on the southern flank of the Cyclops Mountains, this species was taken from a clear, steeply dropping stream flowing in a bed of very large boulders, partially shaded by disturbed rain forest. Based on known collections, D. helleri steuberi occupies the Cyclops Mountains area of freshwater endemism (Area 12) as defined by Polhemus & Allen (2007).

Figures

FIGURE 3. Distribution of certain Dineutus (Rhombodineutus) species on New Guinea. Symbols with grey centers represent previous records; symbols with black centers represent new records presented in this paper.