Species Nanocladius bicolor (Zetterstedt, 1838) and N. distinctus (Malloch, 1915)
Body
The anterior and posterior parapods are separate and bear rows of smooth claws Nanocl bic claws ant pp. Procercus well developed and sclerotized caudally. Two pairs of anal tubules present (Wiederholm, 1983; Moller Pillot, 1984b).
Head
The head length up to 0.38 mm (Moller Pillot, 1984b).
Antenna
The antenna consists of five segments. The blade is shorter than the flagellum. Lauterborn organs are conspicuous. Antennal ratio 1.75 - 2.00 and first antennal segment 56 - 60 µm (Saether, 1977).
Mentum
The mentum has two median teeth and 6 pairs of lateral teeth Nanocl rectin mentum. The ventromental plates are exceptionally long and narrow. The beard is absent.
Labrum
The pecten epipharyngis consists of three spines. SI is simpel (Wiederholm, 1983; Moller Pillot, 1984b) and the premandible with a single or faintly bifid apical tooth (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 body is much larger than that of the small Nanocladius larvae.
N. bicolor agg. can be separated from N. balticus and N. rectinervis by the antennal ratio of 1.75 - 2.00, being greater than in the other species.