Diamesa aberrata

Author: Lundbeck, 1898

Diagnosis (n=3, unless stated otherwise, material in coll. Serra-Tosio)
Exuviae 5.7-6.5mm long.
Cephalothorax: Frontal setae 240µm long (n=1). Precorneal setae 2,3: 140-183; 50-105µm long. Thoracic horn 425-455µm long; ThR 17-23.
Abdomen: Hook row II absent. Total dorsal teeth II-VIII 47-67+; posterior teeth of tergites 40µm long, brown, set on mounds which may be tinged with yellow. Total ventral teeth III-VII/VIII 53+-71+; ventral teeth narrower and/or as pale as or paler than the dorsal. Abdominal tergites II-VIII with at least a median patch of dense small points (031h.jpg). Shagreen points of tergite III 4µm long. Relative length segments IX:VIII:VII = 1.0:0.65-0.71:0.95-1.2 (n=2); relative width segments IX:VIII:VII = 1.0:1.2:1.4-1.5 (n=2). Segment VIII 2.2-2.8 and segment VII 1.7-2.1x as wide as long (n=2). Lateral setae 1-3 of segments II-VII more or less equidistant, stout almost thorn-like, sometimes forked or branched. Lateral setae 1-4 of segment III 140-195; 138-163; 145-190; 95-110µm long.
Note: Colour pale golden or tan with anterior edge of tergites and lateral adhesion marks brown; inner half of paratergites nearly colourless.
Anal segment: Anal lobe ratio 1.3, 1.6 (n=2). Each anal lobe with 3 apical macrosetae, pale, without infuscation; length macrosetae 0.7, 0.8 times lobe length (n=2).

Species keys out at Page 573: Diamesinae 49 Diamesa of the Text Key.

Holarctic species: Widespread in (west) Europe, north Africa.
(For more information see module IdentifyIt – file: Other subfamilies).

Ecological notes
Cool or cold running water; sometimes hygropetric; rarely in northern lakes.