Orthocladius marchettii Rossaro & Prato, 1991

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 : 6-8

Orthocladius marchettii Rossaro & Prato, 1991

O. marchettii Rossaro & Prato, 1991

DESCRIPTION. See Rossaro & Prato (1991, Fig. 14, 15). Often posterior segments V­VIII very dark and anterior segments light, but dark and light segments can be disposed in a variable pattern. In the same population, some pupal exuviae are observed with all abdominal segments light, except an anterior dark band; these specimens have no diagnostic characters to separate them from O. glabripennis . Frontal warts present, but not developed. Thoracic horn 450­480 m long with points on the whole surface, rounded and gently curved at apex. Thorax moderately rough. Pedes spurii B normally developed. Tergites with points all about the same size, on TIII posterior points more developed than the median ones (Fig. 1.1). On TIV­VI median points larger in the middle of tergite, grading in size from middle tergite outwards, particularly in TV. Posterior points on TIII­V extending laterally as far as the apical point band. Field of points on T III­VI extended antero­laterally well beyond anterior muscle marks and grading in size, antero­laterally extended points very small. Abdominal segment VIII with 4/5 lateral setae, the first and the last one often bifid, 3 or 4 lateral setae on segment VII, 3 on segments III­VI. Pedes spurii A present on S IV­VII. Anal lobes always without any taeniate extension of cuticle (Fig. 2.5). Anal macrosetae 250­280 m long, hooked at tips, anal lobes 400­475 m long and 510­555 m wide.

COMMENTS. This species has no taeniate extension of cuticle at the tips of anal lobes and resembles O. glabripennis and O. maius in this respect. The Nearctic species O. nigritus Malloch, 1915 is also described without spurs ( Soponis 1977) on anal lobes. O. marchetti is characterized by the dark pigmentation on abdominal segments. Nonpigmented specimens cannot apparently be separated from O. glabripennis . The species is known to occur only in Italian Apennines, but absent in Central Europe, Italian Alps and Padania lowland (Northern Italy). The species is restricted to running waters.

MATERIAL EXAMINED: ITALY: EMILIA ROMAGNA: Chiavenna stream, tributary of Po river (PC), 10/4/1979, 1 Pex; 8/2/1980, 1 Pex; Tributary of Taro river, Bedonia, 15/5/2001, 1 Pex; Taro river, Compiano, 2/5/2001, 1 Pex; Borgo Val di Taro, 2/ 5/2001, 1 Pex; Bidente stream, 27/3/1979, 1 Pex; Magra stream, 5/3/1981, 1 Pex. ABRUZZO: Tordino stream, valle Teramo, 10/1/1990, 1 Pex; Aterno river, 26/2/1990, 1 Pex; 11/12/1991, 1 Pex; 2/3/1992, 1 Pex; 11/3/1992, 1 Pex; Vetoio spring, 19/3/1992, 1 Pex.