Sergentia coracina

Author: (Zetterstedt, 1850)

Exuviae 7.4-10.6mm long (m=8.9mm, n=44).
Colour: Exuviae darker than Sergentia pe1 and Sergentia prima, comb of segment VIII golden-brown to brown.
Cephalothorax: Cephalic tubercles about 100µm long, more or less cylindrical, truncate and capped with fine spinules. Frontal setae present (120k.jpg). Thoracic horn with 6-10 branches. Thorax with a narrow band of small granules along the suture.
Abdomen: Tergites II-VI with obvious anterior transverse bands of points stronger than those of the median patch. Tergites III-V with median patch narrowed anteriorly, but generally quite broadly attached to the anterior band; anterior band points grading posteriad to median point size; marmoration more discrete than in Sergentia pe1, the circular bare patches separated by three or four points. Tergites III and IV with an apical band of points. Lateral shagreen of sternites III and IV of spinules directed lateral and arranged in irregular longitudinal rows (a good confirmatory character, but sometimes the spinules are irregularly dispersed and occasionally missing altogether). Conjunctives unmarked laterally. Vortex present.
Anal segment: Anal lobes with 54-103 taeniae (m=72.7, n=43); taeniae all similar in size and more or less evenly spaced over the middle two thirds of the lobes, crowded posteriorly into more than one rank.
(Linked adult male: Langton and Pinder, 2003a)

Species keys out at Page 295: Chironomini 192 Sergentia of the Text Key.

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

Ecological notes