Orthocladius van der Wulp, 1874

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 : 3-4

Subgenus Orthocladius van der Wulp, 1874 .

DESCRIPTION OF PUPAL EXUVIAE. Colour variable from transparent to dark, with tones from yellow­gold to brown­black. Pigmentation is often differently distributed on abdominal segments. There is some variation within species, but in some case different pigmentation has taxonomic value. Frontal setae on frontal apotome on small cephalic tubercles; frontal warts ( Saether 1980; Langton 1991) present, more developed in O. pedestris Kieffer, 1909 , but less developed in O. rubicundus (Meigen, 1818) . Thoracic horn elongated, usually with small points, length varying from 200 to 500 m, very long, slender and unarmed in O. frigidus (Zetterstedt, 1838) and in O. vaillanti Langton & Cranston, 1991 ( Caldwell 1998) , enlarged in the middle in O. wetterensis , more or less rounded or pointed to apex in other species. Often the thoracic horn appears to be bent at apex, but this shape does not always have taxonomic value because it can be influenced by mounting position. In some species (e.g. O. pedestris ) it appears clearly bent in all the examined specimens. Posterior rows of hooks always present on T II, relative width of hooks area with differences in species, narrower in O. oblidens (Walker 1856) than in O. obumbratus Johannsen, 1905 . Adhesion (=muscle) marks present on tergites: 2 oblique marks are in the postero­median area and 2­5 less visible marks in the antero­lateral area. Five dorsal setae (D I­V) are present on tergites, three ventral setae (S I­III) on sternites. TII­V with very small points forming an area (=point patch), which may be divided into an anterior, median, posterior and apical field, continuous with ( O. obumbratus ) or well separated from ( O. rubicundus ) each other. T VI with only an anterior, median and posterior field, but T VII­VIII without point fields. The fields of points are more or less developed and extended laterally, and often very small points may be observed extending to the anterolateral corner of abdominal tergites, beyond the adhesion marks. Point patches are present also on sternites (especially S II­III); the points often joined into groups of 2­3 ("Gruppenshagreen"). The small points on the antero­lateral corner of tergites are variable in extension. Attention must be given to distinguish them from similar points on sternites in specimens mounted in dorso­ventral position. The number of antero­lateral adhesion marks and the position of seta D I have low taxonomic value because they are variable characters. The different size of anterior, median, posterior and apical field of points on tergites is emphasised as an easily observable character without substantial variation within species, and thus is a good candidate to be used in taxonomic keys and useful for separating many species.

Usually very small blotches are present at the base of apical points on tergites, but in only one species ( O. pedestris ) are there large brown blotches extending laterally to the apical point area of tergites and postero­medially on sternites. Pedes spurii B present on segment II (absent in O. ruffoi and reduced in O. frigidus ). Pedes spurii A present on S IV­ VII, but reduced on S VII in some species. Five (occasionally four) lateral setae are present on abdominal segment VIII, with variation within species, very well developed in some species (e.g. O. ruffoi Rossaro & Prato 1991 ), sometime the anterior and/or the posterior one bifid, with variation within species. Anal lobes with 3 anal macrosetae, usually strongly hooked at tip, but straight in O. ruffoi , straight or gently curved in O. dentifer Brundin, 1947 . Tips of anal lobes with or without taeniate extensions of the cuticle; when present they have different consistence and have taxonomic value; they can vary from very small, colourless light extensions ( O. ticinoi ), to broken setae ( O. rubicundus ), teeth ( Langton & Cranston 1991), spiniferous processes ( Saether et al. 2000) or well sclerotised chitinous spurs ( Soponis 1977) ( O. obumbratus , O. pedestris ). Additional small taeniate extensions, sometime appearing as a weak fringe of short setae, may be present ( obumbratus , pedestris ): a well developed fringe of setae or hair­like teeth ( Langton & Cranston 1991) is present only in O. vaillanti , a less developed one in O. ruffoi . ALR varying around 1; the ratio between the length of anal macrosetae and anal lobes has taxonomic value.