Kieffer in Kieffer and Thienemann, 1908
Body
Medium sized to large larvae up to 11.5 mm long. Body setae pale and indistinct. The anterior and posterior parapods are separate and bear rows of claws. Procercus is reduced or absent with 4 anal setae and the subapical seta directly on the body. Two pairs of anal tubules present (Wiederholm, 1983).
Head
Antenna
The antenna consists of five segments. Segment 5 longer than segment 4. Segment 3 annulated. Lauterborn organs are small or vestigial Diam insignipes antenna 8.
Mentum
The mentum has one or two median teeth and 7-11 pairs of lateral teeth. The ventromental plates are weak Diam insignipes mentum 8.
Labrum
The pecten epipharyngis consists of five broad scales, SI is simpel and labral lamellae numerous with pointed, serrated or branched apices. The premandible has 5-7 apical teeth and a lateral spine (Wiederholm, 1983).
Mandible
The mandible has an apical tooth and 4-5 inner teeth. The seta interna with appr. 20 smooth to serrated branches (Wiederholm, 1983).
Differential characteristics
Living in flowing water, a mentum with 7 or more lateral pairs of teeth, weak ventromental plate Diam insignipes mentum and simpel SI separate Diamesa and Syndiamesa from all other Orthocladiinae s.l. Diamesa is characterized by a procercus absent or very reduced with 4 setae apically and the subapical seta arises from the body. In Syndiamesa the procercus is not reduced and bears 5-7 anal setae and 2 subapical setae.