Species 3e. Chironomus (Chaetolabis) ochreatus Townes, 1945.

Tendipes (Chaetolabis) ochreatus - Townes (1945)

In BOLD Bin: BOLD:AAP5112

Adult:

Male:
Wing length 3.9-4.6 mm, width 0.93-1.03 mm.  VR about 0.93-0.96.
Head yellowish green; antennae and palps dark.  AR about 3.9-4.1.  Frontal tubercles small, about 5-10 x 8 µm.
Palps (micron): 80 : 72 : 277 : 304 : 420.  About 30-45 clypeal setae.
Thorax greenish, mesosternum and mesonotal vittae brownish yellow, posterior part of postnotum brown.   Setae: Acrostichal - 12; Dorsocentral - 25-26; Prealar - 7; Scutellar, anterior (2 rows) 4+10; posterior 13 (total Scutellar 27).
Legs yellowish green, anterior legs darkened at the knees, tibia and tarsi dark; other legs with tibiae yellow brown shading to black on distal tarsal segments.  Anterior tarsus without a beard.

Leg lengths (in microns) and proportions as below:

 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1690
1580
2480
1225
900
780
355
1.55-1.70
1.07-1.08
2.06-2.11
PII
1810
1740
1062
610
435
283
192
0.57-0.61
1.03-105
 
PIII
1950
2105
1428
850
583
350
228
0.68
0.92-0.94
 
ForeTa5/Ti about 0.21.

Abdomen: Basal segment yellowish green, the rest blackish brown.  Superior volsella club shaped, which is distinctive.  About 9 setae on tergite IX in individual pale areas.  Inferior volsella extending beyond the anal point and to about midpoint of the gonostylus where it begins to narrow markedly.


Male terminalia of C. (Chaetolabis) ochreatus.
Note the club shaped superior volsella.

Female:
Median mesoscutal vitta dark brown and divided longitudinally by a pale line.  Otherwise similar to the male except for the usual sexual differences.  Further data based on one reared specimen:
Wing length 4.98 mm, width 1.40 mm.  VR 0.90.  3-4 Scf on brachiolum, 23-26 setae on squamal fringe.
Head: Antennal segments (micron)(fraction of neck in brackets): 230 (0.28): 160 (0.47): 175 (0.46): 135 (0.43): 295, segments not sufficiently swollen to give obvious necks (see figure below).  AR 0.42, A5/A1 1.28.
Frontal tubercles small, about 9-10 x 12.5 µm.
Palpal proportions (microns): 75 : 60 : 293 : 333 : 426; P5/P4 1.28; P5/P3 1.45.
Width of clypeus 1.9 times the diameter of the antennal paedicel; about 54 clypeal setae.
Thoracic setae: Acrostichal - abt 13; Humeral 5 in a patch + 2 linear and 6 in a loose patch; Dorsolateral - 38-41 (Humeral + Dorsolateral 43-46); Prealar - 8-9; supraalar - 1; Scutellar, anterior row 14, posterior row 21 (total 35).
Leg lengths (in microns) and proportions as below:
 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
Ta4/Ti
PI
1920
1850
-
-
-
-
-
-
1.05
-
PII
2000
1940
1100
590
420
300
230
0.56
1.03
 
PIII
2120
2340
1580
820
610
360
260
0.68
0.91
 

Setae on GcIX - 4; segment X long and narrow (see figure below), about 239 x 27 µm, 8.6-9.4 times longer than greatest width, with 7-8 setae; cercus (below) a rounded square with a small basal extension on the dorsal margin.


Antenna (left) and ventral abdomen (right) of C. (Chaetolabis) ochreatus female.

Pupa:  Length of exuvia about 10.3 mm (male), inner margin of wing case about 2.04 mm; color yellowish brown; with well developed narrow cephalic tubercles (70 x 20 µm) arising from a broad base, with subapical seta about 56-58 µm long; also a large secondary tubercle or frontal wart about 56-68 µm long and 43-48 µm wide at the base.
Basal ring kidney shaped, about 177 x 82 µm, i.e. l/w about 2.1-2.2; 2 vacuoles slightly anterior to it. Abdomen with a central patch of shagreen on segments II-V, grading from posterior 2/3 on seg. II, to whole length of segment on segment V; on segment VI the shagreen is restricted to the anterior third.
Pedes spurii B on segments II and III small; PsA on segment IV 243 µm long ((0.25 of segment length) and 134 µm wide.  Numbers of L-setae on segments II-IV also as usual, the posterior two on segment IV arising reasonably separated.
Hook row on segment II with about 93 hooks, occupying about 42% of width of segment.
Posterolateral spur of segment VIII with 1-2 large spines with 0-3 small spines at their base, all spines closely applied and main spines extended to a fine curved point.  About 142 taeniae in multiple rows on each side of anal lobe.

Fourth instar larva a medium sized thummi-type; length about 12.8-16.8 mm (Female 15.5 (14.8-16.8) mm; male 14.1 (12.8-15.3) mm); posterior pair of ventral tubules longer and coiled (ant. 1.34 (1.21-1.57) mm; post. 1.50 (1.41-1.81) mm), those of the Quebec specimens much shorter than those from Wisconsin.  Anal tubules very large, about 4.5-6.4 times longer than wide, with a constriction about one third from the base (dors: 1120 x 200 µm, vent: 1180 x 170 µm).
Gula region and frontoclypeus usually pale, but some specimens have very slight darkening of both.  Width of frontoclypeus between the antennal bases (ASA of Vallenduuk & Moller Pillot, 1997) about 186-190 µm, greater than the distance between the S4 setae (about 160-175 µm).  Oesophageal opening about 83.5 µm wide and 3.7 times wider than deep.
Mentum (Fig. d) with relatively pointed teeth;  c1 tooth moderately broad with short parallel sides, c2 teeth moderately well seperated (type IB).4th laterals hardly reduced (type I); 6th laterals arising at about the same level as other teeth.
Ventromental plates (Fig. e) about 248-250 µm wide and 3.06-3.38 times wider than deep and 1.08-1.09 times the mentum width; separated by about one third of the mentum width; with about 39-45 striae (Webb et al. 1987).
Premandible (Fig. b)with narrow, sharp outer tooth, often shorter than the inner tooth, which is 4-5 times wider.  Pecten epipharyngis (Fig. c) with about 23.2 (21-25) irregular teeth, with small interstitial teeth (type D).
Antenna (Fig. a) with A1 about 35-44% of the VHL; A2 long, over 1/3 length of A1, which itself is about 3.3-4.3 times longer than wide; ring organ a third to almost half way up from the base; AR 1.95 (1.50-2.27; antennal segment proportions (micron) 154 : 44 : 11 : 18 : 8. i.e. A5 about same length as A3.
Mandible (Fig. f) with 3rd inner tooth partly separated and only moderately pigmented (type IIB); with about 19 (17-2) furrows on outer margin at base; Pecten mandibularis of 13.2 (12-15) taeniae; Mdt-Mat about 28, MTR 0.31-0.47.

Cytology:  3 polytene chromosomes which may have the modified thummi arm combination, AB, CD, GEF; but Keyl pattern very difficult to recognize.
Nucleolus near the junction of arm G with E, arm G generally unpaired;  2 Balbiani rings between nucleolus and end of arm, with another in arm E, found in some cells of one larva only.  No nucleolus in the long chromosomes.
Polymorphism in arms B and F.

FoundQuebec – Lake Opasatica, Rouyn-Noranda (48.17; -79.33).
            Arkansas – Galloway (Townes); White River National Wildlife Refuge, Arkansas (Chordas et al. 2004.)
            Georgia - roadside pond (B. Caldwell, in Epler 2001)            Maine – Lincoln Co. (Townes)
            Massachusetts – Holliston (Townes)
            Michigan – Empire (Townes)
            New JerseyMedford Lakes (Type locality); Chesilhurst; Glassboro (Townes)
            New York -– Lake Sebago, Bear Mountain State Park (Townes)
            Rhode Island – Westerly; Wickford (Townes)
            South Carolina – Greenville, Table Rock State Park, Pickens Co. (Townes)
            Virginia – Four-mile Run; Norfolk Co. (Townes)
            Wisconsin – Little John Jr Lake, Vilas Co. (46.00°N, 89.63°W); Mud Lake, Vilas Co. (46.02°N, 89.62°W).

            At depth of about 4 m amongst Drepandocladus exannulatus, and in pools.

Wiederholm (1979) considered Ch. ochreatus to be a synonym of Ch. atroviridis, but did note that this was subject to confirmation by further analysis.  The presence of the large secondary tubercles in the pupa (above) shows that it is clearly distinct.  Detailed features of the larval ventromental plates are given by Webb et al. (1987).

DNA analysis: Sequence for the mitochondrial CO1 and the nuclear gb2β genes are available.
CO1: Gene bank accession numbers KF278327; KF278328; KF2788351.  Also Barcode sequences in BOLD database.

See also Ch. bitumineus (sp. 2h), Ch. atroviridis (sp. 2i).

[ Return to Index| Go to References ]


Modified: 1 October 2021
Access: Unrestricted
Copyright © 2000-2021, Jon Martin.