Oriental Chironomus: C. bicoloris

Chironomus bicoloris Tokunaga, 1964

There is doubt that this species does occur in the Oriental region. Karunkaran (1969) claimed to have specimens from Singapore, but it is more likely that she had an undescribed species.

Tokunaga's (1964) description of C. bicoloris.

Type data: holotype USNM US66552 adult male, paratype(s) USNM 2 adults male.
Type locality: Dugor, Weloy, Yap Island.

Other than the original descriptions the available material is from northern Australia

Adult:

Male:
Wing length: 3.34-3.76 mm.; wing width 0.82-0.86 mm.; VR about 1.0. Brown spot over crossvein; usually 4, or 3, Scf on brachiolum; 22-23 setae on squamal fringe.
AR about 3.10-3.16.
Frontal tubercles longer than in Micronesian specimens - about 50-60 micron and 2.5-2.8 times longer than wide - longer than the width of two eye facets. Clypeus width about 157-170 µm, about 0.75 of diameter of antennal pedicel; with about 27-33 setae.
Palp proportions (µm): 66 : 64 : 253 : 249 : 436; P5/P4 1.75; P5/P3 1.72.
Thorax green, vittae, postnotum and sternopleuron reddish brown, vittae with 2-3 darker markings on vittae; Setae - about 19 acrostichal; 26-30 dorsocentral; 28-37 scutellar - 12-17 in 1 or 2 anterior rows and 16-20 in posterior row.
Legs with femur and tibia greenish, tarsi yellowish with at least slight darkening of knees and at tips of tarsi.
Lengths (microns) and proportions as follows:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	BR
PI	1460	1405	2275	-	-	-	-	1.62	1.04	-
PII	1540	1485	940	530	390	215	150	0.63-0.67	1.06	-
PIII	1675	1825	1355	750	600	350	155	0.73-0.75	0.93-0.94

Abdomen greenish proximally, anterior segments with proximal dark band which becomes larger in the more posterior segments until whole segment is darkened.

C. bicoloris: Male hypopygium (left) and superior volsella (right)

Setae on tergite IX: 14.3 (13-16) in idividual pale patches within a larger pale patch. Inferior volsella reaching to about the end of the anal point; setae forked.
Superior volsella closest to E(h) type of Strenzke (1959) (see above); gonostylus slender and tapers gently over posterior half.

Female: (based on single specimen from near Sarina Beach, Queensland (AQ.66.1).
Colour yellowish, with brown vittae; legs as in males.
Wing length 3.42 mm., width 0.89 mm.; VR 0.91. 3-4 Scf on brachioum; 17-18 setae on squamal fringe.
Relative length of antennal segments (micron) (proportion of neck in brackets): 164 (0.25) : 109 (0.38) : 124 (0.44) : 118 (0.45) : 182 ; AR 0.35, A5/A1 1.11. . Frontal tubercles about 22 µm long and 2.5 times longer than wide. Clypeus about 1.7 times the diameter of the antennal pedicel, with 35 setae. Palpal proportions (micron) 63 : 48 : 188 : 250 : 385 (P5/P4 1.54; P5/P3 2.05).
Thoracic setae: acrostichal abt 14; humeral 5-6 linear; dorsocentral 22 (Humeral+dorsocentral 27-28; prealar 3; supraalar 1; scutellar with 2 rows - 7 in anterior row and 10 in posterior row (total 17).
Leg lengths (micron) and proportions

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1315	935	1770	860	760	705	340	1.89	1.41	0.73
PII	1265	1140	660	350	250	190	135	0.58	1.11	-
PIII	1355	1380	950	510	410	270	160	0.69	0.98	-

Segment X crescent shaped, about 3.9 times longer than its greatest width and with 9 setae.

Cercus and segment X (at left) of C. bicoloris

Cercus shorter on the dorsal margin, posterior margin slighly curved towards ventral end and merging into the longer ventral margin with a basal bulge.

Found: Micronesia - Caroline Islands: Pelau Islands and Yap Island.
Also found in Queensland - Lake Boemingen and Lake Wabby (25.27°S, 153.80°E), Fraser Island (H. Burton, light trap) (25.15°S, 153.10°E); 3 km w. Sarina Beach (21.40°S, 149.25°E).

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