Chironomus longistylus

Author: Goetghebuer, 1921

Diagnosis (CMD reared specimens, coll. R.S. Wilson (0028/0032/0033).)
Exuviae 7.2-11.8mm long (m=9.7mm, 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 108x110-200x185µm (n=8), conical. Frontal setae 30-82µm long (n=8). Thoracic horn much branched; basal ring 128x60-200x80µm (m=176x77µm, n=9); tracheal patch 100x30-150x40µm (m=134x43µm, n=9); 15-18 tracheoles across; 2-4µm in diameter (n=6). Tracheal 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. Distinct granulation extending posteriad further, still discernible on each side of the oblique hinge line to the scutal hump, where about three small granules project.
Abdomen: Hook row II entire, length of row 0.47/0.53x width tergite (n=2); hooks 68-99 (n=6). 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 in the form of an undivided, usually extensive patch of strong points, the points in each segment increasing in size posteriorly; the point patches increase in extent from tergite II to V. The most posterior points of tergites IV and V short. Points of tergite VIII mainly isolated and irregularly arranged. Seta D4 of tergite VI closer to mid-line than seta D3. Sternites III and IV without a complete anterior transverse band of shagreen. Lateral shagreen bands of sternite III evanescing anteriorly (usually reduced to a median patch), not extended mediad. Sternite IV without lateral shagreen or with a very reduced band. Parasternite II obviously shagreened; III without shagreen; IV may have a few minute points in posterior half. Pleura IV quite densely spinulate; spinules 10-18µm long. Conjunctives IV/V and V/VI less strongly armed, rarely the points spinulate. Comb of segment VIII with 1-4 stout apiculate teeth, set on the end of an elongate ventral cuticular mound which exceeds appreciably the apico-lateral corner of the segment. Lateral taeniae of segments V-VIII: 4,4,4,5.
Anal segment: Anal lobes weakly rounded. Anal lobe with 66-140 fringe taeniae (m=110, n=10), and 1(2) dorsal taenia.

Note: Goetghebuer (1928) records his longistylus from "Belgique, Angleterre". Whereas the pupal exuviae of longistylus sensu Wülker has yet to be found in the British Isles, this form is widespread in Britain and Europe. The male hypopygium accords better with Goetghebuer's original description (1921) fig.196 (see also his fig.88, Goetghebuer, 1928a), appendage 1 being longer and narrower (cf. fig.144C in Pinder, 1978a; fig. 174B in Langton and Pinder, 2003a) than in longistylus sensu Wülker, where it is more club-shaped. Northern and montane specimens are large; brackish-water specimens very small.

Species keys out at Page 206: Chironomini 103 Chironomus of the Text Key.

Holarctic species: Widespread in Europe (arcto-alpine distribution).
(For more information see module IdentifyIt – file: Chironominae).

Ecological notes
Shallow stagnant water.