Nocentini, 1985a
Body
Small to median sized larvae up to 5 mm long. Living larvae red. Claws on the posterior parapods are simpel. No lateral and ventral tubules. Procercus and anal tubules present (Nocentini, 1985).
Head
Antenna
The antenna consists of 6 segments. The blade is shorter than the flagellum. The 2nd segment as long as the 3d segment. Lauterborn organs are absent Saetheria antenna.
Mentum
The mentum has one broad median tooth paler than the 7 pairs of lateral teeth. The first lateral is partly fused with the median tooth. The ventromental plates are as wide or wider than the mentum Saetheria mentum.
Labrum
SI is simpel and labral lamellae are absent. The pecten epipharyngis is a small triangular plate. The premandible with 5 teeth.
Mandible
The mandible without a dorsal tooth, apical tooth and 4 inner teeth present, the basal pairs smaller and partly fused Saetheria mandibl. The pecten mandibularis consists of 5 setae in a transverse row. The seta interna with 4 serrate branches are present (Nocentini, 1985a).
Differential characteristics
Saetheria and Kloosia are the only genera with a 6-segmented antenna and missing lauterborn organs. The body of Saetheria is somewhat slender, but nowhere near as thin as Kloosia.
S. sp. Nocentini differs from S. sp. 9 Lipina by 7 lateral teeth on the mentum, 2nd antennal segment appr. as long as the 3d segment, mandible with 4 inner teeth, pecten mandibularis consisting of a transverse row of setae and premandible with 5 teeth.