(Palmen, 1959)
Body
The anterior and posterior parapods are separate and bear rows of strongly serrated claws Nano balt claws. Procercus well developed and sclerotized caudally. Two pairs of anal tubules present (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The head length is only 0.22 - 0.28 mm (Saether, 1977).
Antenna
The antenna consists of five segments. The blade is shorter than the flagellum. Lauterborn organs are conspicuous. Antennal ratio 1.00 - 1.26 and first antennal segment only 22 - 25 µm (Saether, 1977).
Mentum
The mentum has two median teeth and very indistinct lateral teeth. The ventromental plates are exceptionally long and narrow Nanoc balt mentum. The beard is absent.
Labrum
The pecten epipharyngis consists of three spines, SI is simpel (Wiederholm, 1983; Moller Pillot, 1984b) and the premandible has 3 - 5 apical teeth (Saether, 1977).
Mandible
The mandible has a long apical tooth and 3 inner teeth Nanocl bic mandible (Moller Pillot, 1984b).
Differential characteristics
The exceptionally long ventromental plates are distinctive Nanocl rectin mentum. Prodiamesinae also have very large ventromental plates, but these are usually covered with setae and their larvae are much larger than the small Nanocladius larvae.
N. balticus can be separated from the other Nanocladius species by the antennal ratio of only 1.00 - 1.26. Also the first antennal segment of only 22 - 25 µm is about half as long as that of the other Nanocladius (Saether, 1977).