North American Chironomus: Kiefferulus dux

Species 5r. Kiefferulus dux (Johannsen, 1905)

As Chironomus dux – transferred to Kiefferulus by Beck & Beck 1970
Synonyms: Chironomus obscuratus Malloch, 1915

Adult:

Male - Wing length 2.4 mm long; LR 1.3; AR 2.6-4.8.
Frontal tubercles not observed, but base 5 µm diameter. Fore tarsis with short, sparse beard (BR abt 2).
Pale green. Antennal pedicel ochraceous, flagellum and palps pale brown except at their bases. Thorax ochraceous; legs pale green, brown towards their apices.
Thoracic setae: at least 14 acrostichal; 13-14 dorsocentral; 6 prealar; 2 supra alar; 12 scutellar in a single row.

Male hypopygium and superior volsella of K. dux
Scattered setae on tergite IX (Townes figures about 9, others 1abt 12-13), some in individual spots, others with 2 in a single spot; anal point short, narrow at base. Inferior volsella broad and rounded at end, and reaches to about distal third of gonostylus (longer than illustrated by Townes,1945 - this may be indicative that more than one species is included under this name, as suggested by Epler (2001).

Female: (1 specimen) Color essentially as male.
Antennal flagellum 5-segmented. segment lengths (µm), with % neck in brackets): 220 (0.26) : 135 (0.47) : 152 (0.38) : 132 (0.47) : 252; AR 0.40; A5/A1 1.14.
Head: FT very small abt 5x7.5 µm (i.e. width at base greater than length) Clypeus with about 35 setae; width 1.7x antennal pedicel. Palpal segments (µm) 72 : 66 : 245 : 260 : 380; P5/P4 1.46, P5/P3 1.56.

a. Cercus & TX, b. small Frontal tubercle, c. Antenna

Thoracic setae: Acrostichals 16; Humerals 5-6 (with 2 pairs setae); Dorsocentrals 14 (humerals + dorsocentrals 19-20); Supraalars 1-2; Prealars 6-7; Scutellar 14 in a single row.
Wing length 3.52 mm, width 1.02 mm; VR 0.87.
Leg lengths (micron) and proportions:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1580	1200	2000	1065	875	810	335	1.66	1.32	0.67
PII	1430	1405	825	395	290	190	150	0.59	1.02
PIII	1315	1520	1065	530	425	245	160	0.70	0.87

BR 1.95

4 setae on GcIX; Seg.X abt 147 x 72 µm, 2.04 times wider than greatest depth, with 11-12 setae.
Cercus with rounded outline and a large bulge at base of ventral edge.

Pupa: Length about 7.15 mm (male), 7.97 mm (female). Female antennal sheath 886 µm long, frontal tubules 20 µm high and 20 µm at base. Shagreen at posterior of segment, divided in midline so that each side is roughly triangular.
Abt 55 hooks at posterior of seg II, occupying abt 0.52 of segment width. Pedes spurii A quite large abt 252 µm long and 54 µm wide, about 0.24 of segment length. The spur of segment VIII has a posteriorly extended base with a number of points (about 8) of various sizes: 5-7 stout ones and 3-7 shorter ones, one of which is stout and between the longer spines with a setae inserted above it. About 136 taeniae on each side of anal fin, in about 3 rows distally.

Morphology of female pupa of K. dux: a. cephalic tubercles, b. shagreen of TIII; c. spur.
Fourth instar larva: A typical Kiefferulus larva with only one pair of ventral tubules.  Head capsule somewhat flatter and broader than a typical Chironomus larva.  Gula and fronto-clypeus pale, although some darkening at posterior of frontoclypeus.  Salivary reservoir firmly attached to ls-2, about 73 (66-78) µm wide and 18.5 (18-20) µm deep.
Mentum (Fig. d, below) with 15 teeth, center trifid tooth closer to type IB but c1 tooth broader (damaged in figure below), lateral teeth in an even slope.
Ventromentum (Fig. e, below) with anterior margin crenulate, 230 µm wide and about 4.5 times wider than deep with about 66-67 striae which show a substantial fold close to their posterior origin; median margin more sharply turned down than in other studied species.  The characteristics of the VM were detailed on the basis of SEM photographs by Cranston et al. (1990).  These scans show that, unlike the other studied Kiefferulus species, the striae are divided.
Premandible (Fig. b, below) with 6 teeth, typical of the genus, although the small 6th tooth may be difficult to see amongst the thick setal brush.  Pecten epipharyngis (Fig. a, below)with about 24 irregular teeth.
Antenna (Fig. c, below) proportions (units) 67 : 25 : 13 : 12 : 5, i.e segments 3 and 4 subequeal, A1 about 3.5 times longer than wide, AR about 1.2.
Mandible (Fig. f, below) essentially as a type IIIC of Chironomus, lacking furrows, about 13 taeniae in Pecten mandibularis, MTR about 0.38 (0.36-0.42).

Mouthparts of K. dux larva: a. Pecten epipharyngis, b. Premandible, c. Antenna, d. Mentum, e. Ventromentum, f. Mandible
Cytology: Four polytene chromosomes. The pattern does not allow comparison with the arms of Chironomus, other than the smallest chromosome (below) which seems to be the homolog of arm G as it contains the nucleolus and at least two Balbiani rings. At least one polymorphic complex inversion was observed on chromosome I (at Madison, WI) and simple inversions on IIL (at Dunrobin, ONT) and chromosome IV (at Madison, WI).

Found: Ontario - Copanspin Farm, Dunrobin (45.42°N, 75.87°W), Carleton Co.; Bear Creek 1 km Carlsbad Springs (45.37°N, 75.47°W); Lake Opeongo (Townes)
Florida - Monticello; St. Augustine (both Townes)
Idaho - Cataldo (Townes)
Illinois - Dubois (Type locality of C. obscuratus).
Indiana - La Fayette (Townes)
Iowa - Davenport (Townes)
Louisiana - Mound (Townes)
Michigan - Midland Co. (Townes)
Minnesota - Crookston; Houston Co. (both Townes)
Missouri - Atherton; St. Louis (both Townes)
New Jersey - Moorestown; Westville (both Townes)
New York - Ithaca (Type locality); Amsterdam; Canajoharie; Hudson; Kinderhook, Lake Sebago, Bear Mt. St. Pk.; Niskayuna;
South Trenton; Tuxedo (all Townes)
Ohio - Summit Co. (Townes)
Oregon - (Independence (Townes)
Rhode Island - Westerly (Townes)
Wisconsin - Madison (43.08°N, 89.42°W)

The ventromentum has been studied in some detail by Webb & Martin (1987) and Cranston et al. (1990).

An apparently widespread species, but it needs to be clarified whether there is more than one species included and, if so, how they are distrubuted. Only one specimen is currently in the BOLD database, and the nearest neighbor is another recognised species of Kiefferulus, so provides no evidence of the existence of multiple species.

Epler (2005) suggests the presence of an additional species of Kiefferulus and of Wirthiella in the Southeast:
K. sp. A, in which the ventromental plates essentially touch in the midline, and known only from peninsular Florida. The pupa and adult are stated to be very similar to those of K. dux.
K. sp. B would be placed in Wirthiella and is recorded from peninsular Florida and South Carolina.