Rheocricotopus effusus

Author: (Walker, 1856)

Exuviae 3.9, 4.4mm long (n=2; reared specimens 2.2-2.8mm) (045-1.jpg).
Cephalothorax: Thoracic horn small-toothed (045c.jpg); horn 290, 310µm long (n=2); ThR 5.1-8.2 (m=6.1, n=12).
Abdomen: Tergites III-VIII with restricted shagreen, at least on VII and VIII, with conspicuous large points medially and/or posteriorly. Point patches more or less circular, present on tergites IV-VI; points of point patches small, the longest less than 30µm long, usually shorter than the longest tooth of the posterior transverse rows. Additional armament of tergites IV-VI usually extensive, the points sometimes so strong that the median point patches are somewhat obscured in outline; median point patch on tergite IV at most a little smaller than on VI (045b.jpg). Pedes spurii B on segment II in the form of rounded humps. Segments III-V usually with 4 setae, evenly distributed, but often only 3 and occasionally arranged as in Rheocricotopus fuscipes (045e.jpg). Lateral taeniae of segment VII 4, VIII 5, the fifth as long as the fourth.
Anal segment: Anal lobe ratio 1.7-2.3 (m=2.0, n=10). Anal lobes not drawn out posteriorly into a tooth or spur. Fringe of anal lobe with 14-21 taeniae (n=2; reared specimens 11-18). The three anal macrosetae situated apically on the anal lobes (045d.jpg).
(Linked adult male: Langton and Pinder, 2003a)

Species keys out at Page 672: Orthocladiinae 84 Rheocricotopus of the Text Key.

Holarctic species: widespread in Europe.
(For more information see module IdentifyIt – file: Orthocladiinae).

Ecological notes
Streams and lakes in hilly districts.