Species 2j. C. crassicaudatus Malloch, 1915

This species is a member of the staegeri group erected by Wülker et al. (1971).
In BOLD Bin: BOLD:AAP2996.

Adult Adult redescribed by Townes (1945).

Male:  Wing length - 4.87 (4.35-5.68) mm; VR - 1.03 (1.00-1.05) or 0.97 (0.95-1.00).  AR - 4.52 (4.15-4.87); LR - 1.28-1.32.
Large and very stout  Ground color light or pale brown, thoracic markings ochraceous brown.
Head - frontal tubercles - 57 (35-82) µm; Clypeus of moderate size, clypeal setae - 60 (44-76)
Thoracic setae - dorsolateral - 47 (29-59); prealar - 10 (8-13); scutellar - 48 (36-62).
Legs- pale brown, apices of tibae and of tarsal segments brown.  Fore tarsus with short sparse beard, fore LR - 1.28; mid LR - 0.48; hind LR 0.54.
Leg proportions (units):

Male hypopygium (left) and superior volsella (right) of Chironomus crassicaudatus

Abdominal tergites each with a central brown transverse band with indefinite edges, VI and following segments mostly brown.
Genitalia large and heavy, with Superior volsella essentially an E-type, closest to E(i) of Strenzke (1959), but with a blunter, more rounded end. Inferior volsella bending inwards towards each other and extending well up to past the mid-point of the gonostyle, which is broad and narrows evenly from about a third of its length.

Female:  Townes notes as "similar to male except for the usual sexual differences".

Pupa: Cephalothorax pale yellowish with brown markings, abdomen pale yellowish with brown markings.

Abdomen of pupa of C. crassicaudatus from Sublette & Sublette (1971)

Frontal tubercles acutely tipped, subterminal seta about 70 µm long.
Length 11.7-14.9 mm (Female: about 12.7-13.1 mm, Male: about 11.7-14.9 mm).
About 92-124 recurved spines in unbroken line at apex of tergite of segment II; caudolateral spur of segment VIII with 12-18 spines (female), 9-19 spines (male).
A pupa with over 12 spines on the spur is likely to be C. crassicaudatus.

Fourth instar larva a large plumosus-type, length 21.4 (17.3 -22.8) mm.  Lateral tubules 370 (300-440) µm; Lateral tubules – ant. 2.45 (1.84-3.00) mm; post. 2.06 (1.64-2.48) mm; AT 530 (480-640) µm.  Very dark gular region, pale frontoclypeus.  VHL about 360 (300-400) µm.
Mentum with pointed teeth, c1 tooth broad, c2 teeth well seperated and sharp pointed (type II); fourth laterals slightly reduced(type I-II).
Ventromentum with finely crenullated anterior margin, median edges sharply downturned.  Striae reaching about 2/3 to anterior margin, then replaced be more numerous very fine striae to the margin.
Pecten epipharyngis with 13-20 irregular, conspicuous large and small teeth.  Premandible with teeth approxomately equal in length.
Antena with basal segment about 3.2 times longer than wide (3.09-3.50); Ring organ between one third and halfway up from base of segment; antennal proportions 141 : 30 : 9 : 13 ; 6.
Mandible 260-330 µm long; polymorphic for third inner tooth, which may be type IA or IIB; about 23-26 furrows on the outer surface at the base, Mdt-Mat 25-28 µm, MTR 0.27-0.31; about 16 taenae in the Pecten mandibularis.

Cytology:  3 polytene chromosomes with a modified thummi arm combination. AB, CD, GEF.
Arm G normally paired with a nucleolus near attachment to arm E, with nearby Balbiani ring and sometimes an additional puff.  Second nucleolus in arm B near 4 characteristic bands.
Polymorphism in arms A, B, C and D.

crc A1:  1 - 2c, 10 - 12, 3 - 2d, 9 - 5e, 17d - 13, 4 - 5d, 17e - 19
crc A2:  1a-e, 12-10d, 13-17d, 5e-9, 2d-3, 1f-2c, 10a-c, 4-5d, 17e-19   i.e. a complex inversion
crc B1:  Puff with distal dark bands (groups 8-7) about 1/3 from distal end.
crc B2:  Puff with proximal dark bands (groups 7-8) still about 1/3 from distal end.
crc E1:  3e - 1, 3f - 10b, 12e - 10c, 12f - 13
crc F1:  1 - 6a, 6d - 9 6b - c, 17 - 11d, 19 - 18, 10 - 11c, 20 - 23
crc G1:  Nucleolus and BR near proximal end.

Molecular data.  There is mtCOI sequence in GenBank (e.g. KR085208), as well as specimens in the BOLD database.
The molecular sequence, along with the modified male hypopygium, indicates that this species is less close to the other three species of the staegeri-group.

Found: Manitoba - Lake Winnipeg (Sæther 2012)
            Ontario - Trenton, Ottawa & Point Pelee (41.959°N, 82.518°W) (Townes 1945)
            Arkansas - Marianna, Lee Parish; White River National Wildlife Refuge, Arkansas (Chordas et al. 2004.)

            Florida - Cannon Lake, Polk Co., Lake Apopka, Orange Co. (Frouz et al. 2002), Miccosuccee Lake.
            Georgia - Lagos Pond, nr Athens & 5 ml w Athens, Clarke Co.; Lullwater Lake, DeKalb Co.
            Illinois - 3.5 ml n.e. Mahomet, & Homer Park, Champaign Co.; Peoria, Peoria Co. (Type), (Townes 1945)
            Indiana - Shafer Lake.
            Iowa - Davenport & Kossuth Co. (Townes 1945)
            Kansas - Potters Lake, Lawrence, Douglas Co.; State Park, Leavenworth, Leavenworth Co. (Townes 1945)
            Louisana - Natchitoches, Natchitoches Pa.
            Maryland - Fenwick, Charles Co. (Townes 1945)
            Michigan - Midland Co. (Townes 1945)
            Minnesota - Hennepin Co. & Traverse Co. (Townes 1945)
            Nebraska - no locality (Townes 1945)
            New Jersey - Wildwood (Townes 1945)
            Ohio - Maumee Bay, Toledo (GenBank KP954640).
            Oklahoma - Buncome Creek Bay, Lake Texoma, Marshall Co.; Oklahoma City (Townes 1945)
            Pennsylvania - Philadelphia (Townes 1945)
            South Dakota - Yankton; Lake francis Case; Gavins Point national Fish Hatchery.
            Tennessee - Oak Ridge, Anderson Co.; Reelfoot Lake.
            Texas - Brownsville & Lake Refugio at Twin Mott (Townes 1945)
            Wisconsin - Lake Wingra (43.05°N, 89.42°W), Dane Co., East Horsehead Lake, Oneida Co.

            Lakes and other lentic habitats, where it can be a pest (Frouz et al. 2002)

Identification:  The larva of this species can be recognized by the combination of characters:  large plumosus-type; very dark gula but pale frontoclypeus; greater than 80 striae on ventromentum with a crenullated anterior margin.  Possibly it may be differentiated by the fine striae in the anterior 1/3 to the margin from C. staegeri or C. frommeri.
Although placed in the staegeri-group, the species differs more in both morphology and cytology.  This suggests that the fusion leading to the reduced chromosome number occurred much earlier than those leading to C. staegeri and C. ‘tigris’.

This species was placed in the subgenus Camptochironomus by Beyer (1941), but was not included in that subgenus by later workers.  Morphology and cytology described by Wülker et al. (1971).  Sublette and Sublette (1971) note that the only species that the adult male could be confused with is C. tentans, but this should also include C. pallidivittatus and C. vockerothi, the latter particularly since Rassmussen (1984) queried whether that species might be a hybrid between C. tentans and C. crassicaudatus.
The species can be bred in the laboratory (Hein and Schmulbach 1971; Frouz et al. 2002).

See also  C. staegeri, C. 'tigris' and C. frommeri

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Modified: 266 September 2021
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