(Figs 2, 9, 14)
Type material
Holotype ɗ, NORWAY: Svalbard, Spitzbergen, Vasa Peninsula, Lake Birgervatnet, 79 º 48 'N, 11 º 37 'E, 15 viii 1983, Ø. A. Schnell (ZMBN Type No. 395).
Diagnostic characters
The male imago is separable from the other species of the subgenus by having dense microtrichiae on both dorsal and ventral sides of gonostylus, strongly sclerotized anal point with nearly parallelsided apex, wings greyish clouded with dark squama, ultimate flagellomere more than 650 m long, gonocoxite with both volsellae weakly developed and no sensilla chaetica on tarsi.
Etymology
Named after the collector of the species.
Male imago (n = 1)
Total length 4.50 mm. Wing length 3.17 mm. Total length/wing length 1.42. Wing length/length of profemur 3.13. Coloration dark brown with thoracic markings barely separable from ground colour. Wing pale greyish clouded with squama nearly black.
Head. AR 1.25. Ultimate flagellomere 676 m long. Temporal setae 17, including 6 inner verticals, 6 outer verticals, and 5 postorbitals. Clypeus with 11 setae. Cibarial pump, tentorium and stipes as in Fig. 9. Tentorium 199 m long, 49 m wide. Stipes 184 m long, 75 m wide. Palpomere lengths (in m): 45, 71, 158, 135, 214.
Thorax. Antepronotum with 5 setae. Dorsocentrals 13, acrostichals 14, prealars 5. Scutellum with 14 setae.
Wing. VR 1.07. Costal extension 53 m long. R with 18 setae, R 1 with 5 setae. Squama with 15 setae.
Legs. Spur of front tibia 79 m long, spurs of middle tibia 45 and 41 m long, of hind tibia 86 and 39 m long. Width at apex of front and middle tibia each 53 m, of hind tibia 58 m. Pseudospurs present on ta 1 and ta 2 of mid and hind leg, 34–38 m long. Sensilla chaeticae absent. Lengths (in m) and proportions of legs:
Hypopygium (Fig. 2). Tergite IX with 18 setae including 2 on anal point, laterosternite IX with 8 setae. Anal point 47 m long. Phallapodeme (Fig. 14) 94 m long, transverse sternapodeme (Fig. 14) 143 m long, oral projections well developed, median portion of transverse sternapodeme very weak. Gonocoxite 326 m long, with two weak but distinct volsellae, strong microtrichiae starting close to base and reaching to apex of apical lobe. Gonostylus 113 m long, densely covered with microtrichiae, widest near apex; crista dorsalis apical, truncate; megaseta 19 m long. HR 2.90, HV 3.98.
Comments
A slightly cloudy wing with squama nearly as dark, is also found in at least some specimens of O. (E.) fuscimanus (Kieffer). The wing of the present species, however, is longer than in any other species examined, and the ultimate antennal segment longer than in other species except O. (E.) gelidus. The strongly sclerotised anal point appear to be unique among the members of the subgenus.
Distribution and ecology
The species is known only from the type locality on Spitzbergen, which is among the northernmost lakes on the archipelago. The only chironomid collected in the profundal zone was Oliveridia tricornis (Oliver). Kick samples along the shore yielded larvae of Diamesa bohemani Goetghebuer, Diamesa arctica (Boheman), undetermined Diamesa, Metriocnemus obscurip es (Holmgren) and Oliveridia tricornis. Adults of Diamesa hyperborea Holmgren were collected together with the present species.