Austro-Pacific Chironomus: C. magnivalva adult

C. magnivalva Kieffer, 1917

Placed in the subgenus Camptochironomus by Cranston & Martin 1989, but this is an artificial grouping of species that mate on the substrate and have enlarged male terminalia.
Returned to Chironomus by Bugledich et al. (1999).
Synonyms: Chironomus crassiforceps - incorrect synonymy by Guryev et al. (2001) and Peck et al. (2002).
Tokkunaga (1964) misidentified C. magnivalva from Micronesia as C. crassiforceps.

In Bold Bin: BOLD:AAJ4269
The nearest neighbour is BOLD:ACC5271 which contains C. crassiforceps

Adult:
A greenish brown species with an enlarged hypopygium, typical of species that mate on substrate.

From Freeman (1961)

Male:
Antennal ratio (AR): Kieffer gave the AR as about 2, while Freeman pushed this up to 2.5. However in one specimen that he measured, it is only about 1.5. Tokunaga (1964) gives the AR of Micronesian specimens as 1.55 (1.48-1.65).
Wing Length: 2.54 (2.32-2.83) mm; wing width: 0.64 (0.48-0.68) mm., VR about 1.08 (1.05-1.15); 2.3 (2-3) Scf on brachiolum; 11.1 (10-13) setae on squamal fringe.
Head: Frontal tubercles about 23-36 µm., generally columnar, and about twice as long as wide; 28.6 (19-44) clypeal setae. Palpal proportions (micron): 48 : 46 : 155 : 147 : 213; P5/P4 1.42 (1.20-1.75); P5/P3 1.37 (1.15-1.57).
Thoracic setae: Acrostichals 12.1 (10-13); Dorsocentrals 17 (15-21); prealars 5 (4-6); scutellars in two rough rows, 4-9 in anterior row, 8-11 in posterior row, total 15.3 (13-17).
LR about 1.59.
Leg lengths (microns) and proportions as follows:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1143	1021	1615	800	699	695	341	1.46-1.74	1.04-1.29	1.27-1.67
PII	1172	1149	569	329	266	192	161	0.47-0.52	0.94-1.08
PIII	1323	1338	791	446	396	234	187	0.55-0.69	0.97-1.00

Ant Ta4/Ti - 0.68; FeI/FeII - 0.92-1.03

Illustration of the hypopygium of C. magnivalva

No setae on TIX; anal point downturned with two distinct dorsal ridgesa flattened triangular tip. Superior volsella normal, closest to E(i) type of Strenzke (1959); Inferior volsella also relatively normal, with simple setae on inner margin only, and extending to mid-point or tip of gonostylus. Gonostyle normally broadest at base, but sometimes quite swollen, narrowing slightly and evenly along its length; with numerous spines rather than setae at the tip.

Female:
Coloration essentially as in male; brownish green darkening over the abdominal tergites.
Wing length 2.97 (2.64-3.44) mm, width 0.95 (0.85-1.01) mm; VR 1.05 (1.03-1.13). 2.8 (2-3) Scf on brachiolum; 16.3 (13-20) setae on squamal fringe.
Head: Frontal tubercles about 25-40 µm long and 11-18 µm wide, about twice as long as wide; antennal proportions (micron, with proportion of neck in brackets) 129 (0.26) : 91 (0.39) : 98 (0.39) : 97 (0.45) : 170. AR about 0.40 (0.37-0.45); A5/A1 1.33 (1.15-1.60). Palpal proportions (micron): 48 : 43 : 146 : 168 : 231.
Thoracic setae: about 13 (10-17) acrostichals; 3.85 (3-6) linear humerals; 20.7 (14-27) dorsolaterals; 5.1 (4-6) prealars; 1 supraalar; scutellars in two rows - 6.2 (3-8) in anterior row and 10.6 (9-13) in posterior row.
Mean leg measurements (microns) and proportions as follows:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	BR
PI	1138	954	1513	715	631	645	323	1.50-1.69	1.13-1.24	0.57-0.78
PII	1160	1150	600	325	250	185	155	0.52-0.53	1.00-1.02	-
PIII	1300	1370	860	470	405	230	190	0.62-0.65	0.94-0.97	-

BR 1.38-1.62; FeI/FeII - 0.96-0.99

GcIX with about 4 setae; segment X larger than usual and oval in shape with about 19.5 (14-24) setae. Cercus essentially oval/rectangular with at best a very small basal extension on dorsal side.

Cercus and segment X of C. magnivalva

Guryev et al. (2001) and Peck et al. (2002) referred Australian specimens from the Alligator Rivers region of the Northern Territory to C. crassiforceps. However this is incorrect - see note on the cytology under the larva.

A possible point of difference in the morphology of the males is that, while the gonostyle of C. magnivalva narrows evenly to the distal end, that of C. crassiforceps appears to remain the same width for most of its length and then rounds off.

Molecular Data:
mtCOI AF192212 (originally as C. crassiforceps, but now corrected)
mtcytB AF192181 (originally as C. crassiforceps, but now corrected)
As noted above, specimens of C. magnivalva and those of C. crassiforceps are in different BOLD Bins.

Found: Northern Territory - Island Lagoon, Magela Creek, Alligator Rivers region (12.57°S, 132.88°E).
Queensland - Noosaville; Sarina (25.36°S, 149.20°E); Townesville (Type locality); South Townsville (19.43°S, 146.80°E); Common,
Townsville (19.36°S, 146.70°E).
Also: - Motu Kö, Pukapuka, Cook Islands (10.88°S, 165.51°W) (E.H. Bryan Jr., Bishop Museum).
Cytologically identical material has been collected from Lautoka (17.67°S, 177.50°E) and Laucola Bay (18.25°S, 178.33°E), Viti Levu, Fiji and Punaauia, Tahiti (17.53°S, 149.57°E).

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