(Kruseman, 1933)
Body
Medium sized larvae up to 8 mm long. Very slender larvae, relatively thick in the middle and tapering towards the head and the anal segments. The posterior parapods very long and anal tubules half as long as the parapods. No lateral and ventral tubules (Wiederholm, 1983).
Head
The head is 2 x as long as wide.
Antenna
The antenna consists of 7 segments. The blade is relatively short reaching only to the tip of the 4th segment, Lauterborn organs are absent Robackia antenna 8.
Mentum
The mentum has 2 dark median teeth and 6 pairs of lateral teeth, the 5th lateral tooth smaller than its neighbouring teeth. The ventromental plates are as wide as the mentum with strong striae and a coarsely crenate anterior margin Robackia mentum.
Labrum
SI is simpel and labral lamellae are absent. The pecten epipharyngis is a small triangular plate. The premandible has 4 teeth.
Mandible
The mandible without a dorsal tooth, apical tooth very long with 4 inner teeth. The basal teeth ar larger and fused at their base The pecten mandibularis and seta interna are absent.
Differential characteristics
Robackia, Beckidia, Chernovskiia and Kloosia all have long and very slender larvae. Robackia is the only one with a mentum with paired median teeth Robackia mentum.