North American Chironomus: C. frommeri

Species 2d. C. frommeri Sublette & Sublette, 1971

Syn. Chironomus species 2 - Morrow, Bath, and Anderson 1968 & 1969

This species is a member of the staegeri group erected by Wülker et al. (1971).
In BOLD Bin no. BOLD3004.
i.e. the same as C. staegeri and C. 'tigris'

Adult:

Male - Wing length 3.69-6.22 (5.41) mm; VR 1.00-1.05; AR 4.10-5.30 (4.66); LR 1.24.
Ground color pale yellowish brown.thoracic markings dark brown,
abdominal tergites with a dark central spot, particularly on segments 2 to 5.
Frontal tubercles about 44-82 µm. Clypeus broad, clypeal setae - 48-76.
Palpal proportions (segs 2 to 5) - 5 : 16 : 15 : 25.
Thoracic setae - Acrostichals in a staggered row; 28-76 dorsolaterals; 8-14 prealars; 48-78 scutellars.
Legs pale, some progressive darkening of tarsal segments. Fore tarsi with a sparse beard.
Leg proportions:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	BR
PI	38	39	50	27	17	15	8	1.16-1.35	0.97	4
PII	42	42	23	14	11	7	5	0.54-0.65	1.00
PIII	50	51	35	21	15	9	6	0.65-0.79	0.98

Abdominal tergites with darkening as on thorax, essentially saddle shaped on segments II-III, central in segments IV- V. About 9 setae in a single clear area near the middle of tergite IX.

Male abdomen (a) and hypopygium of lectotype (b) of C. frommeri from Sublette & Sublette (1971)
Superior volsella long, closest to Ei-type of Strenzke, but tending to a knob at the distal end. Inferior volsella long, extending beyond end of anal point to about halfway along the gonostylus, which is moderately swollen and narrows only very gently towards the end.

Female - General coloration as male but with dark markings more extensive.
Wing length 6.08 mm; VR 0.95 (Sublette & Sublette give it as 1.05); squama fully fringed.
Antennal proportions 25 : 17 : 20 : 20 : 35. AR 0.43, A5/A1 - 1.4.
Length frontal tubercles 74 µm. Clypeus broad, 2.2 times width of antennal pedicel. Palpal proportions (segs. 2-5): 5 : 16 : 15 : 22.
Thoracic setae: Acrostichal in one staggered row; dorsocentral (incl. humerals) - 70; prealar - abt 9; supra-alar - 2; Scutellar - anteriorly abt. 60 in strewn pattern, posterior row about 40.
Leg proportions:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	40	40	49	25	16	14	8	1.22	1.0	0.35
PII	45	45	24	13	9	6	6	0.62	1.0
PIII	53	55	38	21	16	9	6	0.69	0.96

Cercus with an essentially curved margin, with a large ventral and a small dorsalbulge - that of the paralectotype female looks a little like a helmet on its side.

Pupa: Length 9.19-14.0 mm (Female: about 12.9-14.0 mm, Male: about 9.2-13.3 mm).
Cephalothorax brown, abdomen pale yellowish with brown markings.

Pupal abdomen of Chironomus frommeri from Sublette & Sublette (1971)
Frontal tubercles short and conical, subterminal seta about 35 µm long.
About 74 - 129 recurved spines at apex of tergite of segment II; caudolateral spur of segment VIII with 7-11 spines (female), 6-12 spines (male).
Swim fin with about 130 flattened taeniae.

Fourth instar larva a large plumosus-type (length: female - about 18.5-22.8 mm; male - about 17.3-20 mm), ventral head length about 290 (330-430)µm.  Ventral tubules long, usually anterior pair longer (Female: Ant. 2.52 mm (2.20-3.00), Post. 2.15 mm (1.68-2.48); Male: Ant. 2.31 mm (1.84-2.64), Post. 1.98 mm (1.64-2.32)).
Posterolateral tubules about 300-400 µm long.  Anal tubules short and relatively cone shaped, less than 1.5 times longer than wide.
Dark to very dark gular region, pale frontoclypeus.
Mentum with pointed teeth; c1 tooth with parallel sides, c2 teeth well developed (type IIA); 4th laterals slightly reduced (type I-II).
Ventromental plates separated by 0.32-0.37 of mentum width, with anterior margin finely crennulated; about 59-88 striae.
Pecten epipharyngis with about 11-19 teeth, larger near the center, diminishing in size laterally.  Premandible with teeth about equal in length, inner tooth about 2.1-2.9 times wider than the outer tooth.
Antenna with basal segment 2.7-4.3 times longer than wide.  At least in the Klamath Lake, Oregon population this character appears to be dimorphic, with some less than 3 times longer than wide (unlesss an artefact of slide mounting), others around 4 times longer than wide (4.0–4.3); AR about 2.14-2.49; antennal proportions 148 : 38 : 8 : 12: 7; A3 shorter than A4, and usually slightly longer than A5.
Distance between antennal bases greater than the distance between S4 setae.
Mandible, with small heel; third tooth relatively distinct, but pale (type IIA), about 26-27 furrows on the outer surface at the base.

Identification: The larva of this species can be recognized by the combination of characters: large plumosus-type, dark gula and pale frontoclypeus, about 60-90 striae on ventromentum, which has a crenullated anterior margin. This does not separate it from C. crassicaudatus or C. staegeri.

Cytology: 4 polytene chromosomes with the thummi arm combination AB, CD, EF, G.
Arm G closely paired with a virtually terminal nucleolus and a central Balbiani ring (BR); chromosome narrows from BR to nucleolus. Nucleolus also in arm B, just distal to the 4 characteristic bands.
Inversion polymorphism in arms C and D.
froA1: 1a-e, 7 - 5e, 3 - 2d, 9 - 8, 13 - 17d, 1f - 2c, 10 - 12?, 4 - 5d, 17e - 19.
froB1: Puff with proximal dark bands (groups 7 and 8) at distal end of arm; nucleolus about group 21.
froC1: not clarified; typical group 3-4 about middle of arm.
froC2: not clarified.
froD1: not clarified.
froD1: not clarified.
froE1:1 - 3a, 10b - 3f, 10c - 13 i.e. as aprilinus, etc.
froF1: 1 - 6a, 6d - 9, 6b-c, 17 - 10, 18 - 23 by transp. 6bc from obtusidens.
froF2: 1 - 5, 17, 6c-b, 9 - 6d, 6a, 16 - 10, 18 - 23.
froG1: virtually terminal nucleolus and median BR.

Molecular sequences:
mtCOI: There are two sequences in GenBank (copied in BOLD Database), Accession nos KF278235 and KF278237.
This species clusters with C. staegeri in BOLD BIN:AAI4303

Found: Quebec - Trois-Rivières.
California - Antioch, Contra Costa Co.: 4 ml e. Olive, Los Angeles Co.; O'Neil Forebay and San Luis Reservoir, Merced Co.;
Lake Crowley, Bishop, Mono Co., Greenfield, Monterey Co.; 1 ml s. Napa, Napa Co.; Lake Elsinore, Riverside Co. (Type locality);
Lake Merced, San Francisco Co.; San Mateo Co.; Lake Dalwigk, Vallejo, Solano Co.
Oregon - Upper Klamath Lake, 1 ml n. Williamson River (42.47°N, 121.57°W); Smith Loop Road, 7 ml. s. Corvallis
(44.50°N, 123.25°W).

Lakes, oxbows and permanent ponds.

The morphology and cytology have been described by Wülker et al. (1971).
Sublette & Sublette originally designated the species authors as Atchley and Martin, 1971, but Spies (2000) designated a lectotype and corrected the author designation.

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

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