Heterotrissocladius marcidus

Author: (Walker, 1856)

Exuviae 4.7-5.7mm long (m=5.2mm, n=26) (039-2.jpg).
Cephalothorax: Cephalic tubercles absent. Thoracic horn 345-515µm long (m=427µm, n=22), small-toothed; ThR 3.2-5.9 (m=5.2, n=21). Wing sheaths without pearl row.
Abdomen: Armed tergites with small points which are gradually a little larger posteriorly on each segment (040a.jpg). Tergites without a median transverse row of strong points. Points on tergites short, giving a finely dotted appearance (039g.jpg). Postero-lateral corner of segment VII rounded. Sternite of male armed with a posterior band of conspicuous points along the evenly curved posterior margin; of female with a pair of triangular projections, each stiffened with an embedded spine (039h.jpg). Pedes spurii A present on segment VII, but may be composed of very small spinules. Pedes spurii B of segment II much wider than high. Three or four lateral setae on segments II-VI, not taeniate; lateral taeniae of segment VII 4, VIII 4, 5.
Anal segment: Anal lobe ratio 1.5-2.4 (m=1.8, n=18). Fringe of anal lobe with 28-36 taeniae (m=31, n=24).
(Linked adult male: Langton and Pinder, 2003a)

Note: A reared specimen, leg. F. Reiss, identified by O.A. Saether as Heterotrissocladius scutellatus is indistinguishable from British specimens of marcidus.

Species keys out at Page 628: Orthocladiinae 40 Heterotrissocladius of the Text Key.

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

Ecological notes
Lakes, ponds and rivers.