Stempellinella flavidula

Author: (Edwards, 1929)

Intermediate in form between Zavrelia pentatoma (q.v.) and Stempellinella brevis. The latter has less extensive armament of tergite II, and less strongly and more diffusely toothed thoracic horn. Most of the available specimens were reared and are a little smaller than wild-caught specimens. Data for reared specimens are included in brackets.
Exuviae 2.5, 2.6mm long (n=2) [2.2-2.7mm (m=2.3mm, n=24)].
Cephalothorax: Cephalic tubercles broad conical, [22, 27µm high (n=2)]. [Frontal setae 125-180µm long (m=143µm, n=8)]. Antennal sheath bases with a small rounded projection. Thoracic horn 330, 345µm long (n=2) [241-315µm long (m=291µm, n=13)]; ThR 11.5, 12.2 (n=2) [11.0-16.1 (m=13.7, n=13)]. Thoracic horn with the apical two-thirds armed with colourless teeth.
Abdomen: [Hook row II 0.21, 0.23x width tergite (n=2)]; hooks 40-45 (n=4) [33-50 (m=40.7, n=17)]. The two point patches of tergite II together forming a trapezoidal area extending to seta D1 or nearly that far. Armament of tergite II less extensive than on III. Tergites III-VI with a median and posterior patch of points on each side of the mid-line, which may be sufficiently extensive to form a single large continuous patch. Small pedes spurii B present on segment II, pleura of this segment unarmed. Lateral borders of segment VIII brown. Occasionally there is an extra tooth just in front of the apico-lateral spur on segment VIII. Lateral taeniae of segments V-VIII: 3,4,4,3.
Anal segment: Anal lobe ratio 1.4 (n=1) [1.34-1.58 (m=1.47, n=10)]. Fringe of anal lobe with 14-19 taeniae (n=4) [10-19 (m=15.7, n=22)].
(Linked adult male: Langton and Pinder, 2003a)

Species keys out at Page 373: Tanytarsini 16 Stempellinella of the Text Key.

British Isles, C Europe.
(For more information see module IdentifyIt – file: Chironominae).

Ecological notes
Shaded trickles and rivulets flowing from chalk springs in beech woods.