Holarctic Chironomus (s.l.) - Einfeldia pagana

Einfeldia pagana (Meigen, 1838)

Originally Chironomus paganus
Syn: Einfeldia synchrona Oliver 1971 (Oliver et al. 1990)
The species relationships in Einfeldia are so confused that any designation of synonymy is tentative at best. While these two species are undoubtedly in Einfeldia, there is insufficient evidence to confidently define them as synonymous.

Specimens claimed to be this species are found in a number of BOLD Bins, but many are actually species of Benthalia
North American specimens are in BOLD Bin: BOLD:AAG5475

A specimen from Japan identified as Einfeldia pagana is closest to BOLD Bin: A specimen from Japan identified as Einfeldia pagana is closest to BOLD Bin: BOLD:AAW3454This bin also contains specimens identified as B. dissidens
From photograph the following can be obtained:
LR1 abt 1.8; LR2 abt 0.6; LR3 abt 0.7.
These data indicate that it is actually a specimen of Benthalia sp. 3.

The description by Yamamoto (1995) seems to be the best description of Japanese material in English. Yamamoto refers to a description in Japanese by Sasa (1993). Some information on the larvae is given Yamamoto et al. (2015), but for the pupa, descriptions of European material must be used.

Adult:

Male: Wing length 3.4-3.9 mm, width 0.9-1.0 mm, 14-24 setae in squamal fringe. VR 0.92 (0.90-0.96); LR 1.72 (1.66-1.76); AR 3.35 (3.00-3.71).
Brownish black, with thorax largely blackish brown, vittae etc. brownish black; legs brown to dark brown. Abdomen uniformly brownish black.
Head: Frontal tubercles minute 2.5-5.0 µm long and 5 µm wide. Clypeal setae not given. Palp segment lengths (1-5) (micron): 67 : 94 : 275 : 198 ; 264; P5/P4 1.33; P5/P3 0.96.
Antepronotum distinctly divided at middle by a conspicuous V-shaped notch, scutal tubercle indistinct, acrostichals normally developed.
Thoracic setae: achrostichals 8-12 (biserial); dorsocentrals 11-14; prealars 6-8; supra alar 1; scutellars 15-23 (biserial).
Leg length and proportions (micron)

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T
PI	1530	1290	2000	1080	810	620	300	1.52-1.63	1.18
PII	1560	1460	890	550	420	300	210	0.58-0.63	1.07
PIII	1690	1830	1230	770	580	390	230	0.65-0.70	0.92

Note: The LRs given by Yamamoto are clearly calculated in a different manner, so the values given by the usual formula (apparently his BV values) are provided.

Gonostyle inflated and abruptly constricted near the apex; anal point broad. Superior volsella with a high base, the chitinised distal part arising below the top of the base and the appearance is not sickle shaped; Inferior volsella relatively thick and straighter than that of E. sasai, bearing recurved setae at the distal end.

Female: Coloration almost the same as male, but antepronotum and ground color of scutum ochreous, vittae black, scutellum pale brown.
Wing length 3.5-4.0 mm; width 1.0-1.2 mm.; VR 0.87 (0.85-0.90); 19-27 setae in squamal fringe.

Antennal proportions (µm): 173 : 113 : 122: 128 : 203; AR about 0.38, A5/A1 abt 1.17.
Frontal tubercle minute, 2.5-5.0 µm long and 2.5-7.5 µm wide. Clypeus with 35-55 setae setae. Palp segment lengths (1-5) (µm): 67 : 90 : 241 : 211 : 321.
Thoracic setae: Acrostichals 7-13 (biserial); dorsocentrals 12-16 (uniserial); supraalar 1.
Leg length and proportions (micron) (values as for males)

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1590	1270	2020	1040	790	600	300	1.45-1.63	1.25	0.47
PII	1640	1460	860	520	390	280	210	0.57-0.62	1.12
PIII	1650	1790	1150	700	540	340	320	0.62-0.66	0.92

Genitalia: Apodeme of VIII sternum well-developed, rounded postero-laterally, joined mesally; segment X with 4-5 setae. Cercus large, oblong.

Pupa: The only information for the pupa seems to be that for European specimens (e.g. Langton and Visser 2003) - sex of exuviae not stated but likely includes both males (smaller specimens with larger cephalic tubercles) and females (larger specimens with smaller cephalic tubercles):
Length of exuvia 7.5-9.0 mm. Cephalic tubercles large, conical, curved, 145-190 µm long and 120-155 µm wide (in males about 3 times longer than width at base; in females about as long as width at base).
Abdomen: Hook row of segment II entire, length of row 0.43-0.52x width of the tergite. Armament of tergites II-IV an undivided, usually extensive patch of strong points, on seg. II extending forward at least as far as setae D1. The patch on tergite VI is more of less reduced. Lateral tainiae of segments V-VIII: 4,4,4,5. Comb, or spur, of segment VIII of 4.5 (2-7) small teeth on a short base that does not exceed the margin of the segment. Fringe of anal lobe with 63-86 taeniae.

Larva: In 2006, Yamamoto published some brief notes on the larva:
One pair of ventral tubules, antepronotum distinctly divided at middle by a conspicuous V-shaped notch, scutal tubercle indistinct, acrostichals normally developed. In 2015, Yamamoto et al. further noted the large oblong fenestra in the frontoclypeal apotome, a feature noted and illustrated for European specimens by Pinder and Reiss (1983) and S5 setae well anterior to the "ring organ" of the dorsal head; the rugosity anterior to the fenestra has not been confirmed in Asian specimens.
The description of North American specimens gives the coloration of the mentum and frontoclypeus as pale.
Mentum with pointed teeth apart from central tooth which may be worn in the available specimen, c2 teeth little more than notches (type I); 4th laterals in line with other lateral teeth (type I).
Ventromentum (A) with a sharply downturned inner edge and a wavy anterior margin. PE (D) with about 12 rather irregular teeth. Premandible (see D) with two teeth of about equal length, inner tooth wider than outer tooth (, below).Antenna (B) with basal segment relatively short, AR = 0.8, about 3.3x as long as wide; A3 relatively long, A4/A3 about 0.8. Mandible (C) with pigmented and clearly separated third inner tooth (type IIIC). No furrows on outer surface near the base.

Cytology: No information is available for Japanese populations.

Other descriptions of Einfeldia pagana indicate that it is a paler species, but it appears that Yamamoto is justified in considering this to be a seasonal variation of color – his specimens were collected in May. However, there is doubt as to whether this material is actually E. pagana, since Yamamoto illustrates the antepronotum to have a distinct V-shaped notch, while the Holarctic keys indicate that the antepronotum is fused. This, together with the fact that there is no Oriental specimen in the same BOLD Bin as the North American specimens, suggests that this material requires a new name.
The presence of this darker form may help explain why the species is confused with the generally dark Benthalia species.

Found: - ?a Holarctic species.
Japan - Yamaguchi, Honshu; Okinawa Island; Kyushu; Lake Hibera, Fukushima;Yoshimi, Shimonoseki (abt 33.9°N, 130.95°E),
Yamaguchi Pref.
There appear to be no specimens in the Chironomid DNA Barcode Database (at January 2020), nor does any Japanese specimen
fall into the same BOLD Bin as the North American specimens (in the absence of any European specimens).
Holarctic distribution (Belgium - region of Liége; Type locality).

Recorded from shallow eutrophic pools.

See also C. (Lobochironomus) dorsalis, E. sasai.

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