Key to some West Palaearctic species of the subgenus Orthocladius s. str.

1 Thoracic horn long, smooth and narrow, brown at base, colourless thereafter (Langton & Cranston, Fig. 1 g). Exuviae brown with transparent inter­segmental bands. Abdominal segments with a dark brown anterior transverse band continued posteriorly along the lateral adhesion marks, the rest of the tergites and sternites paler. Abdominal TII­VI(VII) nearly or completely covered with points between the lateral adhesion marks. On segment VIII two or three lateral setae, at most approach half the segment length. Anal lobes dark, tapered from the middle to the tips.................. 2

­ Thoracic horn length does not exceed 500 m. Armament of abdominal tergites usually much less extensive and posterior abdominal segments are pale (except in O. marchetti). Lateral abdominal setae short, except in O. ruffoi ................. 3

2 Anal lobes rarely with lateral setae, points on tergites generally not extended overall.................................................... frigidus (Zetterstedt)

­ Anal lobes with an extensive fringe of setae, points on tergites extensive (Langton & Cranston, Fig. 5)............................... vaillanti Langton & Cranston

3 Apical macrosetae of anal lobes about as long as the lobes, brittle, not hooked at tip. All five lateral setae of segment VIII particularly conspicuous, over half the length of segment VIII, brown. Pedes spurii B absent. Anal lobes with a lateral fringe of sparse hair­like taeniate extensions of cuticle. Abdominal segments more or less evenly brownish (Langton & Cranston, Fig. 1 e, 2b, 4a), (Rossaro & Prato 1991, Fig. 2 ­3)................................................... ruffoi Rossaro & Prato

­ Apical macrosetae of anal lobes shorter than the length of the lobes and usually hooked at tip. Pedes spurii B on segment II conspicuous. Lateral setae of segment VIII weak.............................................................. 4

4 Posterior point band on TIII extending laterally than the apical band. TIV­V with median points somewhat larger than the more lateral, showing as a more or less circular area within the point patch. Usually setae on SIII forked or branched, this occurring to a lesser extent on S II and SIV...................... oblidens group 5

­ Posterior point band on TIII not extending further laterally than the apical band (in most species equalling the width of the posterior band). Forked or branched setae rare and usually confined to the apical segments............................... 6

5 Apical setae of anal lobes short, less than half the lobe length, almost straight, only slightly hooked at tip (Langton & Cranston 1991, Fig. 4h). Posterior band of T III extending further laterally than the apical band................ oblidens (Walker)

­ Apical setae of the anal lobes longer and curved along their length, hooked at tip (Langton & Cranston 1991, Fig. 4d, Rossaro & Prato 1991, Fig. 6). Posterior band of TIII extending to a lesser extent then the apical band.............. rivinus Kieffer

6 Granulations (a conspicuous row of chitin rings) are present on the tergites laterally on the apical band. A posterior band of granulations (still more conspicuous) is generally (not always) present on sternites also, often in a dark field. Median point band of TIII­ IV generally transverse, that is separate from posterior band, sometimes joined to it laterally, or medially also. Points of median and posterior bands similar in size and form. Anal lobes with apical taeniate extensions of cuticle; which resemble broken setae, the anal macrosetae usually strongly hooked at tip. Lateral setae of the posterior segments short and thin............................ rubicundus (Meigen)

­ No granulation present on tergites and sternites. Median point patch of T II­IV usually completely fused to the posterior band to form a single trapezoidal patch; if transverse, then median and posterior points very dissimilar in size..................... 7

7 Apical part of abdominal segments dorsally without brown blotches outside the apical point band (Fig. 1.1) and ventrally always without brown blotches. Point patches on TIII­V more or less trapezoidal with the points of median and posterior bands about the same size and form, or median and posterior points of different form and size, at least on TIII, or points of median patches on TIII­V grading antero­laterally into fine points (”Shagreen”). ........................................................ 8

­ Apical part of abdominal segments III­VIII on ventral side with large brown blotches, similar blotches are present lateral to apical point band dorsally (Fig. 1.2). TIII­IV with the median and posterior point patches of similar size and form, fused. Exuviae usually very dark. Apical taeniate extensions of cuticle present on anal lobes as well developed chitinous spurs, anal macrosetae hooked at tips....... pedestris Kieffer

8 Anal lobes without apical taeniate extensions of cuticle (Fig. 2.5). Points of the posterior transverse band of TIII similar, larger or smaller ( wetterensis) than those of the median band.................................................... 9

­ Apical taeniate extensions of cuticle of anal lobes always present, either as brown, sturdy, chitinous spurs (Fig. 2 ­4), or as small and colourless teeth (Fig. 2.3). Points of the posterior transverse band of TIII similar or larger (never smaller) than those of the median band........................................ obumbratus group 13

9 Points of median and posterior bands well separated. Lateral setae on posterior segments long and robust, on tubercles...................... dentifer Brundin

­ Points of median and posterior bands continuous.......................... 10

10 Points of the posterior transverse band of TIII obviously smaller than those of the median and apical bands. Thoracic horn broad and contracted strongly in apical half, with small points. Anal lobes without apical taeniate extensions of cuticle, but a lateral fringe of extensions may be weakly developed............... wetterensis Brundin

­ Points of the posterior band of TIII similar to larger than points of the median band................................................. glabripennis group 11

11 Some abdominal segments, especially the posterior segments, very dark, restricted to running waters.............................. marchettii Rossaro & Prato

­ Abdominal segments not markedly coloured, except an antero­lateral band..... 12

12 T IV ­V with points of median patch grading in size from mid­tergite outwards (pale specimens of marchettii also key here), restricted to lentic waters.............................................................. glabripennis Goetghebuer

­ T IV­V with median points somewhat larger than more lateral and showing as a more or less circular area within the point patch..................... maius Goetghebuer

13 Taeniate extensions of cuticle present at the tips of anal lobes as well chitinised spurs, at least 35 m long, generally much more (Fig. 2.4). Anal lobes may be weakly fringed with hair­like lateral taeniate extensions of cuticle in addition to the apical ones. Exuviae brown with darker anterior and lateral bands. Thoracic horn 420­480 m long........................................... obumbratus Johannsen

­ Taeniate extensions of cuticle present at the tips of anal lobes, but colourless and small, 30 m long at most (Fig. 2.3). Exuviae pale yellow. Thoracic horn 240­420 m long ............................................... ticinoi Rossaro & Prato