Orthocladius obumbratus Johannsen, 1905

Bruno Rossaro & Carlotta Casalegno, 2001, Description of the pupal exuviae of some species belonging to Orthocladius s. str. van der Wulp, 1874 (Diptera: Chironomidae: Orthocladiinae), with a new key to species of West Palaearctic region, Zootaxa 7, pp. 1-20 : 9-10

Orthocladius obumbratus Johannsen, 1905

O. obumbratus Johannsen, 1905

O. rhyacobius Kieffer, 1911 ( Langton & Cranston 1991)

O. rhyacophilus Kieffer, 1911 ( Langton & Cranston 1991)

O. dispar Goetghebuer, 1942 ( Langton & Cranston 1991)

O. excavatus Brundin, 1947: 20 ( Langton & Cranston 1991)

Orthocladius Pe 9 Langton, 1984: 155 ( Langton 1991: 190; Langton & Cranston 1991)

nec Orthocladius rhyacobius Kieffer, 1911 , sensu Langton, 1984: 158

DESCRIPTION. See Potthast (1915: 270­271, sub rhyacobius ), Langton & Cranston (1991, Fig.1 b, 3c, 4b). Abdomen about 3.5 m long. Anterior and lateral margin of tergites darker. Frontal warts well developed. Thoracic horn 400­450 mm long, “proximal etwas angeschwollen, distal spitz” ( Potthast 1915: 269). Spines stronger in distal part of thoracic horn, more developed than in O. ticinoi . Thorax rough. Points continuous but not much extended over the tergites, the oral and lateral margins free, but a field of very small points of very variable extension, may be present at the antero­lateral corner, in this case there is a sudden drop in size of points. Posterior and apical points on tergites not more developed than the median and anterior ones. TIII with posterior points not extended laterally to apical points. SII­IV with extended fields of grouped points. Lateral setae: 1 on segment I, 3 on segments II­VI, 4 on segments VII and 5 on segment VIII. Anal lobes with apical taeniate extensions of cuticle, having the shape of 2 brown and sturdy chitinised spurs, often fused at base, at least 35 m long (Fig. 2.4), in addition one or more lighter taeniate extensions are often present, sometime appearing as a fringe of small extensions on lateral margin of anal lobes in caudal part. Anal macrosetae, 215­235 m long, hooked at tip, anal lobes 330­370 m long and 400­460 m wide.

COMMENTS. The pupal exuviae can be easily separated because the length of taeniate extensions of cuticle at the tips of anal lobes is 30 m in O. ticinoi at most, but more than 35 m, generally much more, in O. obumbratus . The points on the thoracic horn and on the abdominal segments are much more extended on O. obumbratus than on O. ticinoi .

MATERIAL EXAMINED: FRANCE: GARONNE river, 10/3/1997, 1 Pex. ITALY: PIEMONTE: Acqualba spring, 10/6/1976, 1 Pex; Elvo stream, Sordevolo, ( BI), 5/5/2001, 1 Pex; Maggiore lake, Angera, 13/2/1996, 1 Pex; Po river, Morano (VC), 16/5/1981, 1 Pex. LOMBARDIA: Brembo river, S.G.Bianco, 9/2/2000, 1 Pex, 5/4/2000, 1 Pex, 16/5/ 2000, 1 Pex, 16/6/2000, 1 Pex, 3/7/2000, 1 Pex; Serina stream, 25/5/1999, 1 Pex, 16/6/ 1999, 1 Pex; Endine lake, 25/2/1981, 1 Pex; Serio river, Ricengo, 24/5/1999, 1 Pex; 31/10/ 1999, 1 Pex, 26/11/1999, 1 Pex, 20/12/1999, 1 Pex, 23/1/2000, 1 Pex, 18/2/2000, 1 Pex, 23/3/2000, 1 Pex, 15/4/2000, 1 Pex; spring Ghiglio near Milano, 13/2/1996, 1 Pex; Lambro river, Asso, 1977, 1 Pex, 26/1/1978, 1 Pex/Lex, 27/12/1979, 1 Pex, 9/11/1995, 1 Pex; P.te Lambro, 12/10/1995, 1 Pex, 9/11/1995, 1 Pex, 21/3/1996, 1 Pex; Olginate lake, 17/2/1977, 1 Pex, 17/2/1977, 1 Pex; Ticino river, Oleggio 14/1/1979, 1 Pex; Boffalora, 1/ 1981, 1 female/Pex/Lex; 4/3/1993, 1 male pupa. LIGURIA: Danè stream, Quiliano (SV), 11/1998, 1 male pupa. EMILIA ROMAGNA: Po river, Corso (PC), 15/12/1975, 1 Pex, 21/ 3/1976, 1 Pex, 12/4/1977, 1 female /Pex, 10/4/1979, 1 Pex; Tributary of Taro river, Bedonia, 15/5/2001, 1 Pex; Bidente stream, 27/3/1979, 1 Pex. MARCHE: Aso river, 17/4/ 1980, 1 Pex. LAZIO: Velino river, 17/3/1990, 1 male pupa, Mignone stream, 26/2/1981, 1 male pupa, 26/2/1985, 1 male pupa. ABRUZZO: Tordino stream, st. 7, valle Teramo, 9/4/ 1991, 1 male pupa; Aterno river, Coppito, 11/11/1989, 1 Pex; 5/2/1992, 1 male /Pex; Tasso stream, P.N.Abruzzo, 20/5/1978, 1 Pex; Sangro river, PNA, Scontrone, st.6, 21 /5/1978, 1 Pex; PNA, Castel di Sangro, st.14, 11 /11/1988, 1 Pex. SARDEGNA: spring near Siniscola, 7/12/1985,1 Pex, 2/1/1986, 1 Pex.

Figures

FIGURE 1. Ventral view (sternite) on the left, dorsal view (tergite) on the right. 1.1: O. marchettii: tergite III with anterior, median, posterior and apical point fields; 1.2: O. pedestris: tergite III with anterior, median, posterior and apical point fields