Medium-sized to large, red coloured, up to 13 mm long. Red larvae.
Frontoclypeal apotome separated from labrum, with round/heart-shaped granular frontal fenestra only in group A (E. pagana and relatives); remaining labral area variably fragmented.
Antenna with 5 segments, diminishing in size distally Lauterborn organs moderately developed, opposite on apex of 2nd segment, with small style. Ring organ in proximal 1/2 of segment 1, seta absent. Blade not reaching apex of antenna.
SI plumose on both sides; SII simple; SIII simple, short; SIV normally developed. Seta premandibularis simple. Labral lamellae fine, without indication of median division. Pecten epipharyngis either simple with few teeth, with multi-layered teeth, or divided into 3 parts, each plate covered with fine hair-like points. Premandible with 2 long, slender teeth, or with additional 2 blunt teeth, with moderate brush.
Mandible with pale, prominent, dorsal tooth, with small additional tooth attached basally, or displaced sideways; with strong apical tooth and 3, or 2, inner teeth. Pecten mandibularis modestly developed, not extending to apical mandibular tooth. Seta subdentalis inserted on ventral surface, simple, extending no further than innermost tooth of mandible. Seta interna inserted on dorsal surface, strongly plumose, 4-branched.
Mentum with simple, robust, sometimes laterally crenate to trifid median tooth, 6 pairs of lateral teeth on each side, with 1st partly fused to 2nd, then evenly decreasing in size laterally or 4th tooth below line of slope. Ventromental plates separated medially by width of median tooth, curved, fan-shaped, with smooth anterior margin; striae complete. Setae submenti simple.
Lateral tubules absent, 1 pair of ventral tubules present in some species.
Our understanding of the composition and relationships within a broad concept of Einfeldia used in the Holarctic key (larvae, pupae and adults) is complicated by uncertainty about the type species (E. pectoralis Kieffer), the existence of several species groups erected for especially the immature stages, and a lapsus in the adult volume concerning E. dissidens that should have read E. longipes.
Following recognition that the broad genus Einfeldia was paraphyletic, there is ongoing reconciliation of the groupings. At present clearly that what was called Einfeldia ‘species group C’ belongs in Chironomus subgenus Lobochironomus. Species group D, essentially for E. natchitocheae Sublette, belongs best with Fleuria, a group of uncertain status and affinities.
Most species remaining in Einfeldia can be divided into two groups (previously ‘A’ and ‘B’) that can be referred to as the ‘pagana’ and ‘dissidens’ groups respectively.
The larvae of the ‘pagana group’ (species group A) are defined thus: Frontoclypeal apotome with a large heart-shaped fenestra; mandible lacking basal furrows, mentum with deeply crenate to apparently trifid median tooth; pecten epipharyngis with simple distal row of teeth, lateral tubules absent; at most 1 short pair of ventral tubules present. This group should be considered as representing Einfeldia in the strict sense (that is, congeneric with E. pectoralis Kieffer).
Larvae of ‘dissidens’ (species group B) lack a frontoclypeal fenestra, have basal furrows on the mandible, a simple or slightly crenate median mental tooth tooth, pecten epipharyngis with distal row of teeth and additional irregular teeth on surface; lack lateral tubules but have a pair of short ventral tubules. In these features the ‘dissidens’ group resembles Chironomus, as also seen in the shared possession of pupal frontal warts.
This ‘dissidens’ grouping termed seems unlikely to be congeneric with a narrowly-defined Einfeldia, but is placed better in Chironomus, perhaps with Lobochironomus. If the group is given a ranked name, then Benthalia, erected for B. kruglovicola by Lipina (1939) is available. Should it be considered that the ‘dissidens group’ is not differentiated from Chironomus subgenus Lobochironomus, then Benthalia would be a senior subjective synomyn of Lobochironomus.
Species groups of Einfeldia and species previously placed therein
- 1. Frontoclypeal apotome with a large heart shaped depression. Lateral tubules absent. At most 1 short pair of ventral tubules present. Mentum with deeply crenate to apparantly trifid median tooth ... Einfeldia sensu stricto [Species group A] (pagana Meigen, pectoralis Kieffer, synchrona Oliver)
- -- Frontoclypeal apotome without heart shaped depression ... 2
- 2. Lateral tubules absent; 1 pair of short ventral tubules present. Mentum with simple or slightly crenate median tooth ... 3
- -- Lateral tubules present; 0 or 2 pairs of, long ventral tubules present. Mentum with trifid median tooth. Outer side of mandible with row of radially arranged grooves ... Chironomus (Lobochironomus) [Einfeldia species group C] (carbonaria Meigen, longipes Staeger and other species)
- 3. Mandible with 3 inner teeth. Pecten epipharyngis simple, with toothlets on surface ...Species group B (dissidens Walker, syn. insolita Kieffer) [perhaps also Chironomus (Lobochironomus)]
- -- Mandible with 2 inner teeth. Pecten epipharyngis in 3 parts, each platelet covered with fine hair-like points ... species group D (natchitocheae Sublette) [perhaps related to Fleuria ?, not congeneric with species group A]
A narrowly-defined Einfeldia for species group A contains Einfeldia pectoralis Kieffer, E. pagana (Meigen) (including synonym E. synchrona Oliver) and perhaps Japanese E. ocellata Hashimoto and Einfeldia kanazawai (Yamamoto, 1996a) (although a later pers. comm. suggests a new taxon is needed for these 2 species). Epler (2001) includes Nearctic E. chelonia (Townes) and recognises a ‘sp. A’ from s.e. USA that may include taxa recognised previously as belonging to E. pagana in the USA. Larvae are found in standing, predominantly dystrophic waters.