Chironomus islandicus

Author: (Kieffer, 1913)

Diagnosis (Material leg. J. Olaffson)
Exuviae 9.0-12.1mm long (n=10).
Colour: Exuviae golden-brown to dark brown. Contrast in colour between thorax and abdomen not so strongly marked: specimens dark anteriorly also have the abdomen infuscated; outer margin of the anal lobes coloured except at base.
Cephalothorax: Cephalic tubercles LxB 80x105-160x120µm (n=6), conical. Frontal setae 45-72µm long (n=6). Basal ring of thoracic horn 145x80-175x90µm; tracheal patch 90x30-120x32µm (n=10); 19/22 tracheoles 1.6-1.8µµm in diameter (very dense and small, difficult to distinguish). Tracheolar patch of thoracic horn without an "eye". Thorax less distinctly granulate: anteriorly the granules are small and distinct; medially most of the granules are somewhat flattened, producing an irregular reticulate pattern, or evanescent.
Abdomen: Hook row II entire, length of row 0.47-0.57x width tergite (n=5); hooks 97-137(n=5). Armament of tergites far less extensive, e.g. on tergite III extending laterally at most only as far as the inner edge of the lateral of the anterior adhesion marks and setae D4. Armament of tergites II-VI not so strongly waisted and with the posterior transverse band not successively increasing in extent to tergite VI; usually reduced on VI. Shagreen of sternite II continuous from postero-lateral corner to seta V5, the region between containing points of similar size to those on each side. Both sternites III and IV with lateral longitudinal bands of shagreen. Sternite IV postero-laterally bare, without a patch of enlarged points. Parasternite II obviously shagreened. Pleura of segment IV spinulate. Comb of segment VIII with 2-7 stout teeth (n=10), set on the end of an elongate ventral cuticular mound which exceeds appreciably the apico-lateral corner of the segment. Lateral setae long: on IV longest seta 150µm or longer, on V longest taenia at least 450µm long. Segment VIII with 5 lateral taeniae.
Anal segment: Anal lobe with 102-137 fringe taeniae (n=8).

Species keys out at Page 203: Chironomini 100 Chironomus of the Text Key.

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

Ecological notes