Diamesa arctica

Author: (Boheman, 1865)

Diagnosis (n=1, material in coll. ZSM)
Exuviae 5.4mm long.
Cephalothorax: Frontal setae 150µm long. Precorneal setae 1-3: 62; 245; 150µm long. Thorax granulate. Thoracic horn 355µm long; ThR 18.
Abdomen: Armament of tergite II consists of dense points extending at least for half the width of the tergite and posteriorly at least as far as the anterior adhesion marks. Tergite II rarely with less than 7 teeth in tooth row; tergites VI and VII dorsally each with 4-10 teeth. Total dorsal teeth II-VIII 60; best developed dorsal teeth less than 50µm long, black, set on a broad golden mound. Total ventral teeth III-VIII 75+. Tergites with a band of points behind the tooth row; points of tergites III-VII spreading posteriorly outside the anterior adhesion marks, extending the point patch towards the postero-lateral corner, progressively more extensive on succeeding segments (031d.jpg). Points of tergite III about 5µm long. Relative length segments IX:VIII:VII = 1.0:0.7:0.9; relative width segments IX:VIII:VII = 1.0:1.2:1.3. Segment VIII 2.5 and segment VII 2.3 times as wide as long. Lateral setae of segments II-VII long; setae 1-4 of segment III 112; 115; -- 120; 55µm long.
Anal segment: Anal lobe ratio 1.4. Each anal lobe with 3 macrosetae; length macrosetae 0.75x lobe length.

Species keys out at Page 580: Diamesinae 56 Diamesa of the Text Key.

Holarctic species: (arctic) N Europe (including Iceland).
(For more information see module IdentifyIt – file: Other subfamilies).

Ecological notes
Far northern streams.