Orthocladius (Orthocladius) excavatus Brundin, 1956

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 : 80-81

Orthocladius (Orthocladius) excavatus Brundin

( Figs 7–9)

Orthocladius excavatus Brundin, 1947: 20 .

Orthocladius (Orthocladius) excavatus: Brundin 1956: 104 ; Fittkau et al. 1967: 362; Soponis 1977: 53; Ashe & Cranston 1990: 205; Yamamoto 2004: 60.

Orthocladius (Orthocladius) obumbratus: Langton & Cranston 1991: 247 pro parte, nec Johannsen 1905: 281.

Material examined. CHINA: Guizhou Province, Fanjing Mountain, Huguo Temple , 3 males, 2.viii.2001, light trap, R. Zhang .

Diagnostic characters. The species is distinct in having virga, pointed triangular superior volsella, and inferior volsella robust with dorsal part relatively long and narrow. It can be separated from the very similar O. rhyacobius by having much higher fore leg ratio.

Description. Male (n = 3).

Total length 2.78–3.35 mm. Wing length 1.43–1.75 mm. Total length / wing length 1.68–1. 91. Wing length / length of profemur 1.98–2.29.

Coloration. Head brown. Thorax dark brown. Antenna, legs and abdomen yellowish brown.

Head. AR 2.10–2.20. Ultimate flagellomere 530–580 µm long. Temporal setae 11–12, including 4 inner verticals, 3–4 outer verticals and 4 postorbitals. Clypeus with 5–9 setae. Cibarial pump, tentorium and stipes as in Fig. 7. Tentorium 123–150 µm long, 22–32 µm wide. Stipes 128–147 µm long, 52–55 µm wide. Palpomere lengths (in µm): 22–25, 42–52, 88–113, 84–108, 133–178. Length ratio of palpomeres 5/3 1.39–1.60.

Wing ( Fig. 8). Anal lobe moderately developed. VR 1.06–1.11. Costal extension 23–40 mm long. R with 3–8 setae, other veins bare. Squama with 9–11 setae.

Thorax. Antepronotum with 5–9 setae. Dorsocentrals 11–14, acrostichals 10–16, prealars 3–4. Scutellum with 8–10 setae.

Legs. Spur of fore tibia 47–57 µm long, spurs of mid tibia 21–25 µm and 18–25 µm long; of hind tibia 48–58 µm and 18–25 µm long. Comb of 10–11 setae, shortest seta 20–25 µm, longest seta 37–45 µm. Width at apex of fore tibia 37–43 µm, of mid tibia 35–38 µm, of hind tibia 40–48 µm. Pseudospurs present on ta 1 and ta 2 of mid and hind leg, 20–26 µm long. Lengths (in µm) and proportions of legs in Table 3.

Hypopygium ( Fig. 9). Tergite IX including anal point with 8–12 setae. Laterosternite IX with 6–10 setae. Anal point 45–50 µm long, 25–33 µm wide. Phallapodeme 68–78 µm long; transverse sternapodeme 80–100 µm long, oral projections well developed. Gonocoxite 188–212 µm long, superior volsella rounded, inferior volsella with dorsal part covering most of ventral part. Virga tapering, 25 µm long. Gonostylus 93–100 µm long; crista dorsalis long and low; megaseta 10–12 µm long. HR 1.98–2.12, HV 2.78–3.04.

Remarks. The specimens keys to O. obumbratus Johannsen in Soponis (1977), which however, has not been found in the Holarctic region. Langton & Cranston (1991) synonymized O. rhyacobius and O. excavatus Brundin with O. obumbratus Johannsen. However , the three species are at present regarded as valid, with O. obumbratus restricted to the Nearctic region. Many species of Orthocladius s. str. are not identifiable with certainty and further material is needed to show whether O. obumbratus is present in the Palaearctic. Wang (2000) recorded O. obumbratus from Henan province, while after re-examining the specimens, we consider it as a misidentification of O. (O.) excavatus Brundin.