Oriental Chironomus: C. acerbiphilus

Chironomus sollicitus Hirvenoja 1962

Adult Described originally from Finland, on the basis of the adult male and female.
Japanese material described by Yamamoto 1997, on the basis of the adult male only. Some additional data from original description.

Male: Wing length 3.2 mm (Eur. 4.4-5.5mm), width 0.9 mm., VR 1.09.  AR 3.51-3.60 (3.69-4.29).  L.R. 1.49-1.56 (1.36-1.58).
Coloration: Head brown, antennal pedicel dark brown.  Thorax with antepronotum yellow, mesonotum ochreus, scutal vittae dark brown, postnotum dark brown.
Legs predominantly yellowish brown, apical part of ta1 and ta2 brown, other tarsi completely brown.  Abdomen predominantly brown, anteromedial and lateral portions of TI, posterior margins of TII-VIII pale, genitalia entirely brown.
Head: Frontal tubercle small. Palpal proportions (micron) 65 : 80 : 180 : 240 : 370.
Clypeus with 33-34 setae, prementum with 1 seta.
Thoracic setae – 0-1 lateral antepronotal; acrostichal - 18-23 (8-23); dorsocentral - (32 (25-53)); prealars 5-6 (5-9); supraalar – 1 (0-2); scutella 33-34 (29-55) irregularly triserial.
Leg lengths and proportions (micron):

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta5/Ti
PI	1350	1240	1890	980	780	680	310	1.49-1.56	1.09	0.25
PII	1400	1350	850	500	350	250	150	0.65	1.04
PIII	1600	1750	1250	750	550	350	200	0.71	0.91

BR (Europe) 2.58 (1.83-4.00)

Hypopygium of C. sollicitus from Yamamoto (1997)

TIX with 5 setae in multiple clear fields (5-13 setae in European specimens).
Anal point long and slender, slightly expanded posteriorly and bill-like in lateral view, Superior volsella of S-type of Strenzke (1959) with 7-9 setae on the base. Inferior volsella long, straight, nearly parallel-sided, extending to tip of anal point, with about 20 recurved setae on apical half, some of which are forked near the tip.

Female: Japanese specimens not known, data from European specimens of Hirvenoja (1962).
Coloration essentially as in male. Wing length 5.2 (4.8-5.5) mm. Thoracic setae: acrostichal – 24 (18-32); dorsolaterals – 47 (32-60); prealars – 7 (6-11); supraalars 1 (0-4); scutellars – 49 (39-65). Fore leg measurements relative to length of tibia:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1.19	1.0	1.57	0.75	0.62	0.57	0.24	1.48-1.68	1.19	0.57

BR 1.64 (1.43-2.17)

Found: JAPAN - Koshunai, Bibai, Hokkaido; Noboribetsu Hot Spr. (42.29°N, 141.08°E), Hokkaido (BOLD & GenBank).
Type locality – Riihimäki (60.83°N, 24.83°E), FINLAND
Other record: Rondane nasjonalpark (61.9814°N, 9.8048°E), Dovre, Oppland, NORWAY (BOLD).

Has similarities to C. trinigrivittatus but differs in the shape of the anal point and the Superior volsella.

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