Paratanytarsus dimorphis

Author: Reiss, 1965

Diagnosis (Material in coll. ZSM)
Exuviae 4.1-5.5mm long (n=12).
Cephalothorax: Cephalic tubercles weakly swollen mounds. Thoracic horn 125-338µm long (n=8); ThR 8.3-16.3 (n=7). Thoracic horn seta 30-45µm long (n=8) (133g.jpg). Posterior thoracic mound with a finger-like projection (133h.jpg). (In general this is a good diagnostic character, but while the projection is usually large and conspicuous, in some specimens it is reduced to a tiny conical tubercle which can be rendered invisible by the way the exuviae is mounted.) The longer of the anterior dorsocentral setae less than 120µm long. Dorsocentral setae simple (rarely one or two forked or branched)
Abdomen: Tergite III with a patch of spines on each side in the posterior half; IV with a single, broad oval antero-median point patch; point patches of V paired (133f.jpg). Comb of segment VIII 38-55µm wide; with 4-13 marginal teeth (n=8). Lateral taeniae of segments IV-VIII: 1/2,2/3,4,4,5.
Note: Specimens collected in Spring lack the lateral longitudinal bands of spines variably developed on tergites IV and V in Summer.
Anal segment: Fringe of anal lobe with 25-36 taeniae (n=7) (133i.jpg).
Note: A further difference between this species and Paratanytarsus dissimilis and Paratanytarsus inopertus (as also note under Paratanytarsus natvigi) is the shape of the anal lobe: in dimorphis the outer margins are straighter and end posteriorly in an obtuse angle, the fringe ending at the angle or just internal to it, whereas in dissimilis and inopertus the lobes are rounded, with the fringe continued around the apex onto its inward facing margin.

Species keys out at Page 388: Tanytarsini 31 Paratanytarsus of the Text Key.

W Europe.
(For more information see module IdentifyIt – file: Chironominae).

Ecological notes