Diamesa bertrami

Author: Edwards, 1935

Diagnosis (n=7, unless stated otherwise, material in coll. ZSM (incomplete) and coll. ZMBN)
Exuviae 4.1-5.8mm long (n=6).
Cephalothorax: Frontal setae 128-200µm long. Precorneal setae 2,3: 133-180; (50)120-160µm long (n=6). Thoracic horn 240-425µm long; ThR 13.8-24.
Abdomen: Posterior tooth row of tergite I usually represented or indicated, less than five teeth are present. Total dorsal teeth I/II-VIII 51-90; dorsal teeth brown, broad triangular, set on squat golden mounds. Total ventral teeth III-VII/VIII 54-91. Points of tergites III-VII restricted to between the anterior adhesion marks though they may spread outwards a little between the anterior and posterior adhesion marks (031c.jpg). Shagreen points on III 3.5-5µm long. Relative length IX:VIII:VII = 1.0:0.71-0.77:1.1 (n=1/2); relative width segments IX:VIII:VII = 1.0:1.2-1.3:1.7 (n=1/2). Segment VIII 2.3-3.0 (n=3) and segment VII 2.4 times as wide as long (n=1). Lateral setae often very variable in position on the same exuviae, e.g. setae 1 and 2 close together on anterior segments, but setae 1-3 more or less equidistant on posterior segments. Lateral setae 1-4 of segment III (40)80-123; 95-120; -- 110-135; 85-115µm long (n=5).
Note: Pale tan to golden; anterior transverse apodeme margined anteriorly with a pale brown stripe; lateral adhesion marks brownish; apical brown part of the teeth about 35µm long.
Anal segment: Anal lobe ratio 1.25-1.42 (n=4). Each anal lobe with 3 macrosetae; length macrosetae 0.76, 0.83 times lobe length (n=2).

Species keys out at Page 569: Diamesinae 45 Diamesa of the Text Key.

Holarctic species: Widespread in Europe, also northwest Africa (Ashe and Cranston, 1990a).
(For more information see module IdentifyIt – file: Other subfamilies).

Ecological notes
Cold running water.