Species nC. stigmaterus Say 1823

Tendipes (Tendipes) stigmaterus - Townes 1945.

Texas, New Mexico populations are in BOLD Bin No. BOLD:AAW3998
California, Arizona populations are in BOLD Bin No. BOLD:AEC0831
The nearest neighbor Bin is BOLD:AAN5315, identified only as Chironomus.

Some of the available data (e.g. BARCODE data) suggests that there are two species under this name - one in New Mexico and Texas (and Florida and the type locality??), the other in California and Arizona.
However further data from other parts of the relatively broad distribution are needed to clarify the true situation.

Adult (mostly from Sublette & Sublette 1974)

Male:
Wing length 4.06 (3.20-5.02) mm.  VR 1.00-1.01 (0.99-1.00).
Pale greyish brown; lighter portions of thorax with a greenish tint; abdomen brown, darker towards the apex and paler near the incisures.
AR - 4.3 (4.00-5.17).  Frontal tubercles large, about 0.08 mm long and 1.7 times longer than width at base, clypeus small, about width of antennal pedicel with 22-38 setae; palp proportions (units) 10 : 8 : 16 : 24 : 40. P5/P4 1.67, P5/P3 2.5.
Central portion of pronotum strongly produced, no mesonotal tubercle.  Thoracic setae - acrostichal in 2 staggered rows; dorsolaterals - about 18 in 1-3 rows; prealars - about 4; scutellar with posterior row of about 18 setae, anteriorly with about 12 smaller setae in a random pattern.
Legs with apex of the tibiae and basal tarsal segments brown; fore tarsi with long heavy beard, LR1 - 1.41 (1.33-1.49); LR2 - 0.58 (0.55-0.63); LR3 - 0.72 (0.68-0.75); BR - 6 (5.0-7.0).
Tergite IX with about 15-16 setae in individual pale areas.   Male genitalia: Superior volsella long and slender, E-type, between h and i, of Strenzke (1959).  Inferior volsella, with forked setae, reaching to about the tip of the broad anal point, which is broad at the base and narrows evenly to the tip.  Gonostylus only moderately swollen, narrowing gently from midway to distal 1/4 in the above Texas specimen, while the SEM in Sublette & Sublette (1974) is more swollwn and narrows over post 1/3 to 1/4 and the IVo reaches to 3/4 along the gonostylus (origin not identified).

Female:
No detailed description available - basically described as similar to male except for sexual differences.  From the figures in Sublette and Sublette (1974), the following characters can be adduced:
Antennal proportions (units, propn. neck in brackets); 15 (0.25): 10 (0.30): 10 (0.30): 9 (0.28): 22.  AR abt 0.5, A5/A1 abt 1.5.  Clypeal width about 1.2 times width of antennal pedicel; about 27 clypeal setae.
GcIX ovoid with about 6 setae.  Seg. X about 0.4x wider at widest point than length of segment, with about 9 setae. Cercus longer than deep, with rounded posterior margin and a swelling at base of dorsal margin.

Pupa: Mean total exuvial length 9.67 mm (male 9.27 (8.21-11.01); female 10.22 (7.99-12.30).  Cephalic tubercless of male about 1.4 times longer than the basal width, with a subapical seta.  The scanning e-m photograph of the frontal apotome shows faint indications of structures which could be frontal warts.  Integument blackish.  Thorax finely papillose; recurved hooks simple, sometimes with a slight barb near the center of the row; 95 (80-116) in females, 78 (60-91) in males.  Distinctive rugose stripes on abdominal segments IV-VI.  Posterolateral spurs with 5 (3-8) closely applied spines.  Anal fringe with a distinct sexual difference in number of flattened setae: 103 (88-117) in males, 117 (94-139) in females.


Pupal cephalic tubercle (above) and spur (below) from a Texas male.

Fourth instar larva a medium to large plumosus-type.  Length: female 14.5-16.8 mm, male 12.7-15.3 mm).  Ventral tubules long with posterior pair longer (Anterior: fem. 2.6-4.1 mm, male 2.0-3.6 mm; Post. fem. 3.6-5.5 mm, male 2.1-4.1 mm).  Lateral tubules 330-730 µm.  Anal tubules (from a Portales male) dorsal 582 µm long x 228 &3181;m wide; ventral 531 µmm long x 202 µm wide (both 2.6 times longer than wide).
Darkened gular region and frontoclypeus (which may be darker in center) (Sublette and Sublette 1974 state that only the gula is darkened).  Mentum of type I, with somewhat rounded teeth, which in trifid center group causes c1 tooth to narrow at base (type IB or IIA).
Ventromentum about 242 (210-268) mm wide and 5.7 (3.8-4.2) times wider than deep; 1.2 (1.06-1.39) times wider than the mentum; with about 53.4 (47-60) striae, VMR 0.31-0.38; IPD about 0.32-0.41 of mentum width.
Pecten epipharyngis with 15.8 (12-19) sharp teeth (type A or B).  Premandible with broad teeth, inner tooth about 3-4.5 times the width of the outer tooth which usually narrows to a broad point, but in a Californian specimen it narrowed sharply to a fine point.  Outer tooth often slightly lonnger.
Antenna with A1 about 3-3.94 times longer than wide; RO about 0.3 (0.25-0.40) up from base; AR - 2.28–2.72; A2/A1 abt 0.18-0.25; segment lengths (micron) 141.5 : 31.5 : 8.5 : 14 : 7.
Mandible with 3rd inner tooth well developed and partially to fully dark (type IIIB-C); about 16.1 (14-19) furrows on outer surface near the base; 11-12 taeniae in the Pecten mandibularis; Mdt-Mat 40.1 (35-45); MTR 0.42-0.50.

Cytology:  4 polytene chromosomes with the thummi arm combination AB, CD, EF, G.
Arm G closely paired except where heterozygous.  Californian populations have 2 interstitial Balbiani rings (BRs) in arm G, but some of the alternative sequences present in other areas appear to have only one BR because the other is inverted to a terminal position where it is difficult to see.  Nucleolus is about the middle of arm D.  Inversions known in all arms, and some populations are quite polymorphic (Hilburn 1979).
sti A1:    1a-2g, 8-9, 13a-f, 3f-2h, 6a-3g, 12c-10, 14-17d, 6b-7, 17e-19
sti A2:    1a - 2c, 15 - 14, 10 - 12, 3g - 6a, 2h - 3f,13f-a, 9 - 8, 2g-d, 16 - 17d, 6b - 7, 17e - 19
sti A3:    approx 1a - 2c, 15 - 14, 10 - 12, 3g - 6a, 2h - 3f, 13f-a, 9 - 8, 2g-d, del 16,17a-d, 6b - 7, 17e - 19
sti A4:    approx 1a - 2c, 15 - 14, 10 - 11, 3i-g, 12c-a, 4 - 6a, 2h - 3f, 13f-a, 9 - 8, 2g-d, 16 - 17d, 6b - 7, 17e - 19
sti A5:    approx 1a-f, 11e - 10, 14 - 15, 2c - 1g, 12a-c, 3g - 6a, 2h - 3f, 13f-a, 9 - 8, 2g-d, 16 - 17d, 6b - 7, 17e - 19
sti B1:    Puff with distal dark bands (groups 7 and 8) near end of arm; BR in group 22, near characteristic 4 bands (24 - 26)
sti B2:    Inversion of region around BR, about groups 21 - 23
sti C:      Four sequences are known, only C1 and C2 common
sti D1:    Only common sequence of the three known
sti D2:    Inversion of distal third of arm
sti D3:    Inversion of region immediately around the nucleolus
sti E1:    1 - 3e, 8 - 5, 9 - 10b, 4 - 3f, 10c - 13;                ie. as maturus(differs from aberratus by In8-5)
sti E2:    approx 1 - 3e, 8 - 7h, 6e - 7g, 6f - 5, 9 - 10b, 4 - 3f, 10c - 13
sti E3:    approx 1 - 3e, 8 - 5, 9 - 10b, 4hg, 4a-f, 3f, 10c - 13
sti E4:    approx 1 - 3e, 8 - 5, 9 - 10b, 4 - 3f, 10c - 12b, 13f - 12c, 13g
sti E5:    approx 1 - 3e, 8 - 5c, 13a - 10c, 3f - 4, 10b - 9, 5ab, 13b-g
sti E6:    approx 1 - 3e, 8 - 6f, 4a-h, 10b - 9, 5 - 6e, 3f, 10c - 13
sti F1:    1a - 10d, 17d - 16a, 11 - 15, 18a - 23f              ie. derived from aberratus by In11-5
sti F2:    1 - 4, 6a - 5, 6b - 10, 17 - 16, 11 - 15, 18 - 23
sti F3:    1 - 4, ?-?, 6b - 10, 17, 14h - 11, 16d-a,15a-i, 18 - 23    (could be 1 - 10 or 1 - 4, 6a - 5, 6b - 10)
sti F4:    approx 1 - 8b, 14d - 11, 16 - 17, 10 - 8c, 14e - 15, 18 - 23
sti F5:    approx 1 - 10, 17 - 16, 11a-c, 11i-d, 15, 18 - 23
sti F6:    approx 1 - 5, 7a - 6a, 6b - 10, 17 - 16, 11a - 15i, 18 - 23
sti F7:    approx 1 - 10, 17 - 16, 11a - 15i, 18 - 20g , 22d - 20h, 22e - 23
sti G1:    Two BRs, one near each end of arm
sti G2:    Inversion of two thirds of the arm; takes one BR to terminal position
sti G3:    Inversion of the region around the other BR of G1
sti G4:    Inversion of slightly more proximal region than in G3, but in G2
sti G5:    Inversion of about half the arm from G1
sti G6:    Small inversion sharing distal break of G4 and within the region of the G4 inversion
sti G7:    Duplication of small proximal region of G2
sti G8:    Small inversion of G1, proximal to, and sharing proximal breakpoint of, G2

Found: Numerous populations in:
        Arizona - Tucson (32.32°N, 110.82°W), Pima Co.; Douglas (Townes, 1945)
        California - Hayward, Alameida Co.; Napa, & 1 mile s. Napa, Napa Co.; Riverside, Riverside Co.; Dolwig Lake, Vallejo, Solano Co.;
        Davis, Vacaville, Cutler, Oildale, Ontario, Cerritos, Palm Springs, Blythe (all Hilburn 1979)
        Florida - Lake Miccosukee (Alberta Lake), Leon Co.; Biscayne Bay and Ft. Lauderdale, Miami-Dade Co.; Charlotte Harbor, Charlotte Co.;
        Jacksonville, Duval Co.; Lake Worth and West Palm Beach, Palm Beach Co. (all Townes, 1945)
        Louisiana - Many, Sabine Co.
        Nebraska - Oak Creek at Lincoln (Townes 1945)
        New Mexico - Portales (33.42°N, 103.33°W), and 4 ml S. Portales, Roosevelt Co.; Santa Rosa, Guadalupe Co.; Roswell & Torrence Co. (Townes 1945);
        Lordsburg, 74. km w Quincey, Alamogordo (all Hilburn 1979)
        New York - Worlds fair Grounds, Flushing (Townes 1945)
        Ohio - Summit Co. (Townes 1945)
        Pennsylvannia - Type specimen
        South Dakota - (from P.L. Hudson?)
        Texas - Brackenridge Expltl Station, Austin, Travis Co.; Galveston & San Antonio (Townes 1945); Broncho, Fredericksburg, Van Horn,
        Davis Mountains, Marathon, Lubbock, Petersburg, Bronte, Junction, Nacogdoches (all Hilburn 1979)
        Mexico - Tlahualilo (Townes 1945)

        Often in sewage oxidation ponds, windmill tanks, etc.

Morphological description by Sublette and Sublette (1974).  They note that the pupa has distinctive rugose stripes on the abdominal tergites.  Morrow, Bath and Anderson (1968) described the egg mass as arcuate, with more than 900 eggs, and 50% of egg masses with an enlarged capitulum.
Cytology described by Martin and Wülker (1974).  The work of Hilburn (1979, 1980) suggests the Californian populations are a distinct species from those in Texas and New Mexico.  The specimens in the BOLD bin from California or Arizona are in one Bin, while those from Texas are in the other.
A comparison of the sequences of 5 specimens from California, one from Arizona and 2 from Texas indicates 23 base differences in the Barcode region:

 
base.
California/Arizona
C A A A A T A T C A C C C G T C A T C C T C A
 
Texas
A G G G G C C G T G T T T A C T G C T T C T G


Note that, as appears common between Chironomus species, many of these differences are in the 3' half of the sequence, such that a short Barcode (550 bp) would be missing 6 of these differences.
Little morphological data on the possibility of two species is available, since Sublette & Sublette (1974) do not identify the source of illustrated material and only a few larvae are available for study.  These latter suggest there may be differences in some characters, e.g. antennal characters.  Obviously more material from other regions is needed to determine whether the two groups are really distinct species or simply extremes of geographical clines.

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Modified: 7 October 2021
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