Polypedilum laetum

Author: (Meigen, 1818)

Exuviae 4.8-6.2mm long (n=7).
Cephalothorax: Cephalic tubercles weakly rounded mounds; frontal setae 45-55µm long (n=3). Thoracic horn 8-branched. Thorax with conspicuously large granules near suture (112b.jpg).
Abdomen: Length hook row II 0.59-0.63x width tergite (n=4); hooks 66-94 (n=7). Tergites II-VI with obvious anterior transverse bands of points stronger than those of the median patch. Armament of tergite II continuous, the median point patch broadly joined to the anterior transverse band or narrowly separate from it (125j.jpg). Armament of tergites III-V discontinuous: at least the anterior transverse point band separate from the postero-median patch, which is narrowed anteriorly to a median point (occasionally here narrowly joined to the anterior band). Median points of tergite III similar in size to those of the apical band; median points of II hardly smaller. Posterior point band of tergites IV-(V)VI continuous (the posterior band may be fused to the median point band to produce a marmorate trapezoidal patch), but may be narrowed medially. Apical bands of segments III and IV complete. Tergite VII without trace of a median point patch. Sternite I without two antero-lateral armed humps. Conjunctives with points no larger than those of the anterior transverse bands of the tergites. Pedes spurii B II well-developed. Vortex present. Comb of segment VIII an elongate compound spur. Lateral taeniae of segments V-VIII: 3,3,4,4, well-developed.
Anal segment: Anal lobes without a dorsal seta. Fringe of anal lobe with 26-43 taeniae (n=7).
Note: This form is very widespread throughout the West Palaearctic; it is variable and may represent more than one species.
(Linked adult male: Langton and Pinder, 2003a)

Species keys out at Page 328: Chironomini 225 Polypedilum of the Text Key.

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

Ecological notes
Fast flowing rivers.