(Meigen, 1818)
Body
Medium sized larvae. Living larvae reddish. No lateral and ventral tubules (Wiederholm, 1983; Moller Pillot, 1984a).
Head
The head capsule is shining with a length of approx. 375 µm. The gula is pale. 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 Pol laetum ant pict9. Lauterborn organs distally on the second segment. The blade reaches the distal apex of the 4th segment. The 2nd segment (approx. 15 µm long) is almost 2 x as long as the 3d antennal segment.
Mentum
The mentum has 2 median teeth and 7 pairs of lateral teeth. The median teeth are not larger than the first lateral teeth Pol laetum ment9. Ventromental plates finely striated with a rounded lateral margin.
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 2 inner 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. laetum can be separated from the other Polypedilum by:
Median mental teeth not larger than the first lateral teeth and 2nd antennal segment almost 2 x as long as the 3d segment.