Chironomus pe18

new form

Diagnosis (material leg. E. Franquet.)
Exuviae 7.6-8.9mm long (n=4).
Colour: Brownish exuviae with darker brown markings. 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 120x90-160x152µm (n=4). Frontal setae 44, 70µm long (n=2). Basal ring of thoracic horn 130x65-150x72µm; tracheal patch 88x24-92x28µm; 12-15 tracheoles across (n=3); 2-3µm in diameter. Tracheolar patch of thoracic horn without an "eye". Thorax smooth, or clearly granulate anteriorly only, with or without a few large granules near suture.
Abdomen: Hook row II entire, length of row 0.56-0.63x width tergite (n=3); hooks 87-107 (n=3). Armament of tergites reduced, 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. Points of tergites III-VI gradually larger over posterior half of tergite. Sternite III (and less extensively, IV) with an anterior transverse band of shagreen; on III the shagreen may spread posteriad for a short distance. Parasternite II obviously shagreened. Pleura of segment IV extensively armed with relatively large spinules: about 20µm long, 1µm broad at base. Comb of segment VIII with 1-4 teeth (n=4), set on the end of an elongate ventral cuticular mound which exceeds appreciably the apico-lateral corner of the segment. Segment VIII with 5 lateral taeniae.
Anal segment: Anal lobe with 89-98 fringe taeniae (n=4).

Form keys out at Page 187: Chironomini 84 Chironomus of the Text Key.

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

Ecological notes
Stagnant arm of Rhône, Arles.