Chironomus (Chironomus) decorus Johannsen 1905

Figs 44A–F

Diagnosis. Generally large larvae, 13–16 mm; head including gular area yellowish brown, posterior margin blackish brown; dorsally frontoclypeal apotome without suture; labrum as in Fig. 44A; SI seta plumose; pecten epipharyngis single dentate plate with teeth gradually becoming smaller laterally; antenna (Fig. 44B) 5-segmented, AR 1.9; mandible (Fig. 44C) with 3 inner teeth, with the basal one being pale, radially arranged basal striations; mentum (Fig. 44D) with trifid median tooth, 6 laterals, 2 nd lateral is smaller and joined to 1 st lateral, 4 th lateral slightly smaller than 5 th; VM plates (Fig. 44E) with anterior margin smooth; basal ridge of maxilla slightly convex with interrupted margin; posterior end of abdomen as in Fig. 44F; abdominal segment 7 with laterodistal tubules present, segment 8 with two pairs of long curled ventral tubules.

Notes. Using Epler (2001) the larva keys out to the C. (C.) decorus group which includes several Nearctic species where either the larvae haven't been associated or the cytological species have not been morphologically described as larvae or both.

Ecology and habitat. In the study streams they only occurred in pools often in large numbers. The C. decorus of this group is tolerant of pollution (Hudson et al. 1990).

Sampling sites. Killarney, Arrowhead and Algonquin Provincial Parks, the Parry Sound and Muskoka Districts.

Nearctic distribution. Canada: Ontario.