Tvetenia duodenaria

Author: Kieffer, 1922

Exuviae 2.8-3.4mm long (n=4).
Cephalothorax: Thoracic horn 385-465µm long (n=5), of Eukiefferiella form, with a swollen base and long apical filament (050h.jpg); length base 0.16-0.19x length horn (n=4); ThR (base) 2.0-2.6 (n=4). Pearl row present.
Abdomen: Posterior transverse tooth row present on tergites II-VII(VIII).
Anal segment: Anal lobes without taeniate fringe.

Species keys out at Page 724: Orthocladiinae 136 Tvetenia/Dratnalia of the Text Key.

Holarctic species: Fennoscandia.
(For more information see module IdentifyIt – file: Orthocladiinae).

Ecological notes
Far northern streams.