Chironomus (Camptochironomus) biwaprimus Sasa

Adult (from Sasa & Kawai 1987)

Male
Length 6.96-8.11; wing length 3.58-4.05; VR 1.02-1.06.  AR 3.17-3.89
LR: Ant. 1.34-1.58; mid 0.50-0.56; hind 0.58-0.64.  BR 1.6.
Coloration unusual - antennal shaft brown, hairs brownish yellow;
ground color of scutum greenish yellow or pale yellow, vittae dark brown;
legs with femur and tibia largely yellow with a narrow apical dark ring;
tarsi darkening from brown to dark brown.
Head with relatively small frontal tubercles 22 micron long, 14 micron wide.
Thorax: Antepronotum united and expanded in the middle, without lateral setae.
Setae: Acrostichal 6-14; dorsolateral 19-36; prealar 6-10; scutellar 24-36 in a double row.
Legs: Front tibia with 4 subterminal setae arising on a rounded terminal scale.  Details of leg segments not given, only LR and BR (no beard).

Hypopygium (above) typical for the members of the camptochironomus-group, apparently closest to C. tentans.  No setae shown in centre of TIX.  Anal point parallel sided, possibly ridged, reaching just past the base of the gonostyle; Superior volsella essentially straight, not reaching the end of the anal point; Inferior volella long and gently curved with thick setae along the inner margin of the distal third; reaching two thirds along the dististyle, which is broad and narrows from about the distal third of its length.

Female

Possible female of C. biwaprimus
Photo by T. Iwasawa

I have been unable to obtain a copy of a description of the female, only copies of figures.
Coloration probably similar to that of the male.
A photograph identified as a female of this species from Sagamihara, Japan shows a greenish yellow patch on each side at anterior of thorax.
Antennal proportions (approx): 20 : 14 : 13 : 13 : 20; A5/A4 abt. 1, AR 0.33.
Frontal tubules not shown (but would be small).
Palpal proportions (approx): 14 : 5 : 19 : 17 : 30 ; P5/P4 abt 1.8; P5/P3 abt 1.6.
Clypeus shown with about 34 setae.
Legs with tibia and femur yellowish, tarsi brown.
Abdomen probably with a pale band at posterior of each segment.

Head (a), spermathecae (b) and cercus (c) of C. biwaprimus female
Sasa & Kawai (1987).

Cercus shown approximately triangular with an obvious proximal bulge.

Pupa: no information.

Fourth instar larva:  A moderate sized, up to 20 mm, plumosus-type larva.  Lateral tubules well developed, about 255 (200-320) µm long.   Anal tubules nearly as long as the posterior prolegs and are constricted in the middle, dorsal pair longer (abt 280-380 µm) and narrower (2.7-3.0 longer than wide); ventral pair about 250-280 µm long and.4-times longer than wide.
Gula dark on posterior half, frontoclypeus dark, particularly towards the rear.
Mentum with broad c1 tooth, closest to type IIB but c2 teeth more separated; 4th laterals hardly reduced (type I).
Ventromental plates separated by about a third of the mentum width (IPD), about 3-3.3 times longer than depth to base of striae; about 48-49 striae; VMR 0.40-0.41.
Pecten epipharyngis with about 14 teeth of type B.
Distance between the antennal bases greater than that between the S4 setae, which are separated by about 72% of the frontoclypeus width.
Antenna with A1 about 3.2 times longer than wide and 0.4 of the VHL; RO about 0.4 up from base of segment, AR about1.93 (1.6-2.12) 2.14; segment proportions (micron): 135 : 32 : 10 : 13 : 8.  A1/A2 = 4.22; A2/A1 = 0.24; A4/A3 = 1.3.
Premandible with teeth coming to broad points (type D), inner tooth about four as wide as the outer tooth.
Mandible about 250 µm in length, third inner tooth pale and incompletely separated (type 1A); about 21 furrows on the outer surface at the base and probably normally about 14 setae in Pecten mandibularis although one mandible of an available specimen had about 18 generally narrower setae.  MTR about 3.0.

Cytology:  Four polytene chromosomes with the Camptochironomus cytocomplex combination AB, CF, DE, G.  Specimens available did not have particularly good chromosomes, but some banding patterns could be determined.    Arm G may have a nucleolus but main nucleolus is in a long chromosome, probably near the centromere of the AB chromosome.  One heterozygote, probably in arm B.

Found: JAPAN Type locality - Lake Biwa (35.33°N, 136.17°E), Honshu. The descriptions suggest there may be two species involved, as 1 specimen is much smaller than the 4 others;  Lake Kasumigaura (36.42°N, 140.39°E); NEIS, Tsukuba (36.08°N, 140.08°E), Yatabe, Ibaraki.
Possible locality: Sagamihara, Kanagawa (35.59°N, 139.28°E), Honshu.