Orthocladius (Orthocladius) rhyacobius Kieffer, 1911

Kong, Fanqing, A. Saether, Ole & Wang, Xinhua, 2012, A review of the subgenera Euorthocladius and Orthocladius s. str. from China (Diptera: Chironomidae), Zootaxa 3537, pp. 76-88 : 84-86

Orthocladius (Orthocladius) rhyacobius Kieffer

( Figs 17–19)

Orthocladius rhyacobius Kieffer, 1911: 181 , 182; Brundin 1947: 22.

Orthocladius (Orthocladius) obumbratus: Langton & Cranston 1991: 247 in part, nec Johannsen 1905: 281. Material examined. CHINA: Inner Mongolia Autonomous Region, Mordaga National Forest Park, 1 male, 8.vii.1987, sweep net, X. Wang.

Diagnostic characters. The species is characterized by the presence of virga, pointed triangular superior volsella, and inferior volsella robust with dorsal part relatively long and narrow. It can be separated from very similar O. excavatus Brundin by having a much lower antennal ratio (1.4–1.7 as opposed to 2.1–2.2) and a much lower fore leg ratio (0.59–0.68 vs. 0.71–0.79). However, O. obumbratus has similar measurements, but has a slight costal extension.

Description. Male (n = 1).

Total length 4.38 mm. Wing length 2.45 mm. Total length / wing length 1.79. Wing length / length of profemur 2.66.

Coloration. Head and thorax dark brown. Antenna, legs and abdomen brown.

Head. AR 1.67. Ultimate flagellomere 750 µm long. Temporal setae 12, including 3 inner verticals, 3 outer verticals and 6 postorbitals. Clypeus with 9 setae. Cibarial pump, tentorium and stipes as in Fig. 17. Tentorium 176 µm long, 40 µm wide. Stipes 212 µm long, 73 µm wide. Palpomere lengths (in µm): 40, 57, 123, 110, 172. Length ratio of palpomeres 5/3 1.40.

Wing ( Fig. 18). Anal lobe well developed. VR 1.10. Costal extension absent. R with 8 setae, other veins bare. Squama with 26 setae.

Thorax. Antepronotum with 5 setae. Dorsocentrals 15, acrostichals 3, prealars 6. Scutellum with 18 setae.

Legs. Spur of fore tibia 57 µm long, spurs of mid tibia 25 µm and 24 µm long, of hind tibia 59 µm and 26 µm long. Comb of 11 setae, shortest seta 26 mm, longest seta 56 µm. Width at apex of fore tibia 53 µm, of mid tibia 52 µm, of hind tibia 63 µm. Pseudospurs present on ta 1 and ta 2 of mid and hind leg, 24–30 µm long. Lengths (in µm) and proportions of legs in Table 6.

Hypopygium ( Fig. 19). Tergite IX including anal point with 14 setae. Laterosternite IX with 10 setae. Anal point 35 µm long, 15 µm wide. Phallapodeme 105 µm long; transverse sternapodeme 138 µm long, oral projections well developed. Gonocoxite 250 µm long, superior volsella triangular, inferior volsella with dorsal part narrow, ventral part extended below. Virga present, 48 µm long. Gonostylus 115 µm long, crista dorsalis long and low; megaseta 14 µm long. HR 2.29, HV 3.30.

Remarks. The species apparently keys to O. obumbratus and O. excavatus in Soponis (1977). However, O. rhyacobius is not included in the key.