Asian Chironomus (s.l.) - Benthalia species 1

Benthalia species 1

Description by Sasa (1985b), drawing on information in Sasa & Hasegawa (1983), as Chironomus (Einfeldia) dissidens - the larval mentum indicates that this is not the species in BOLD Bin: BOLD:AAW3454.

Adult:

Male:  Ground color of dark brown or nearly black, vittae shining black, scutellum dark brown, postnotum black; wings unmarked; femora, tibia and tarsi I of all legs yellow, tarsi II-V brown; abdominal tergites uniformly dark brown or nearly black.
Wing length 2.40 (2.23-2.53) mm.  AR 2.64 (2.60-2.68); 15.8 (13-19) setae in squamal fringe.  Frontal tubercles (fig. A) prominent, 48 µm long and 18 µm wide.
Thoracic setae: Antepronotals absent; acrostichals - none; dorsocentrals 15.3 (12-18); prealars 5 (4-7); scutellar 15 (13-19) in two rows.
LR1 1.85 (1.84-1.86), Ta5/Ti 0.29;  LR2 0.56 (0.54-0.58);  LR3 0.73 (0.71-0.75).
No tarsal beard: BR1 2.1; BR2 3.1 (1.9-4.0); BR3 3.8 (3.2-4.1).
Hypopygium as in figure G, H, I, Superior volsella comprised of a high setigerous basal portion with a bare, hook-like apical process (very similar to that of Einfeldia);Inferior volsella expanded apically, with short recurved setae.

Female: Coloration essentially as in male. Wing length 2.75 mm; squamal fringe with 19-20 setae.
Frontal tubercles (fig. B) prominent, nearly conical 40 µm long, 32 µm in diameter.
Thoracic setae: Antepronotals absent; acrostichals - none; dorsolaterals 14-15; prealar - 5; scutellar 18 in two transverse rows.
LR1 1.81, Ta5/Ti 0.24; LR2 0.56; LR3 0.73. Tarsal hairs short: BR1 1.3; BR2 2.0; BR3 3.2.
Cerci (Fig. J) nearly square with rounded corners 62 µm long and 60 µm wide.

Pupa: Length of abdomen 4.90 mm. Pupal cuticle generally almost colorless, but slightly brown in parts. Respiratory organs as in Chironomus. Distribution of spines, spinules and hairs and other features as in Sasa's figure; the number of spines and and shape of the patches differ considerably by the segments. Segment VIII without a scale or spur, anal fringe of 78-92 taeniae.

Larva: Gross morphology not described, but likely it has only 1 pair of ventral tubules.  No information on anal tubules, but base of preanal hair tuft low and flat with 2 long slender setae, while preanal hair tuft comprises 7 on each side.
Mentum (Fig. N) 144 µm wide with 13 teeth, c1 highest and widest, 4th laterals narrower and shorter than neighbours.  Ventromentum (Fig. N) fan shaped, 138 µm wide and 70 µm deep; the figure shows about 55 striae.
Antenna 4 segmented, but figure (L) shows 5; lengths segs 1-4 (micron): 60 : 28 : 6; 16; RO about middle of segment 1; antennal blade at base of seg. 2 about 1/3 length of that segment.
Figure (K) shows numerous very small teeth in Pecten epipharyngis, and premanbible with very short teeth (very worn?).
Mandible (Fig. M) 142 µm long, with a comb near the tip.  Procercus (O) not pigmented, 7 anal setae.

Cytology: Not known for Asian material.

Found: Japan - Shore of Lake Ikeda (31.23°N, 130.57°E), Kagoshima Prefecture, Kyushu; Yoshimi, Shimonoseki, Yamaguchi Pref., and Toyama Pref., both Honshu; Okinawa Island (both Sasa 1985b); Lake Shoji, Mt Fuji region, both Honshu.
Also considered the same species as collected by Sasa and Hasegawa (1983) from Okinawa and associated with polluted waters.

DNA analyses:
MtCOI barcode sequence from the Lake Ikeda and other localities is available from GenBank through the "Chironomid DNA Barcode Database" (CDBD).

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