Kieffer, 1921
Body
Medium sized larvae, up to 7.5 mm long. Living larvae red. No lateral and ventral tubules (Wiederholm, 1983; Moller Pillot, 1984a).
Head
The head capsule is shining with a length of approx. 359 µm. The gula with a dark basal spot. The eyes are rounded, small and apart Pol bicr eyes. Anterior margin of frontal apotome is straight without a subapical pit, but with anterio-lateral lobes on which the S3 is inserted. Labral sclerite 1 absent, sclerite 2 present.
Antenna
The antenna consists of 5 segments. The fifth segment is a lauterborn organ Pol bicren antenna pict9. Regular lauterborn organs distally on the second segment. The blade reaches beyond the apex of the 5th segment. The 3d segment is unusually short and much shorter than the 4th segment.
Mentum
The mentum has 2 median teeth and 7 pairs of lateral teeth. The median teeth are larger than the first lateral teeth and about equal as the 2nd lateral Pol g nub mentum 8.
Labrum
SI is plumose on both sides and labral lamellae a single plate with numerous distal teeth. The pecten epipharyngis with 3 small plates with distal teeth Pol pecten epiph. The premandible has three teeth.
Mandible
The mandible with a dorsal tooth Pol g nub mandible, apical tooth dark and 2inner teeth. The pecten mandibularis is present and seta interna with plumose branches.
Differential characteristics
Two median and 7 pairs of lateral teeth on the mentum Pol g nub mentum 8, with Lauterborn organs on the second segment and shining dorsal headcapsule will separate Polypedilum from all other genera except from Parachironomus which however has a completely different mentum Parach arc mentum.
P. bicrenatum can be separated from the other Polypedilum by:
Dark gula and the antenna with very short 3d segment and 5th segment as a lauterborn organ.