(Kieffer, 1909)
Body
Small larvae up to 4 mm long. On body segments 7-10 the L4 setae with alternating simpel and plumose setae. The anterior parapods are separate and bear a row of claws. Procercus present and two pairs of anal tubules are longer than the posterior parapods (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The head length is 0.28-0,37 mm (Moller Pillot, 1984b).
Antenna
The antenna consists of four or five segments depending on whether segment 3 is weakly or entirely subdivided. The blade is longer than the flagellum. Lauterborn organs are distinct.
Mentum
The mentum has two median teeth and 4-5 pairs of lateral teeth. The ventromental plates are very long, covering one or more pairs of lateral teeth. The beard is extremely large, radiating from the center Synor semiv mentum 8. The setae are branched at the apex.
Labrum
The pecten epipharyngis consists of three large scales, SI is simpel and the premandible is simpel (Wiederholm, 1983; Moller Pillot, 1984b).
Mandible
The mandible has an apical tooth and 3 inner teeth. The seta interna is absent. The inner margin of the mandible with a spine (Wiederholm, 1983).
Differential characteristics
The extreme large beard is distinctive for Synorthocladius Synor semiv mentum 8 and Parorthocladius Parorthocl mentum. Synorthocladius can be separated from Parorthocladius by having a mentum with two median teeth instead of three.