Brundin, 1949
Body
Medium sized to large larvae up to 6.5 mm long. The anterior parapods are separate. The two posterior parapods bear rows of claws. Procercus and two pairs of anal tubules present (Saether, 1975; Wiederholm, 1983).
Head
The head length is 0.36-0.43 mm and postmentum is dark and contrasting with the rest of the gula Heterotr marcidus head ventr (Saether, 1975).
Antenna
The antenna consists of seven segments Heterotr marcidus antenna. Segment 3 much shorter than segment 4, the blade is much shorter than the flagellum (Saether, 1975d). Lauterborn organs reduced or absent (Wiederholm, 1983).
Mentum
The mentum has one median tooth and 5 pairs of lateral teeth. The first pair stands free from the median and second lateral teeth. The ventromental plates are large and the beard is absent Heterotr mae mentum.
Labrum
The pecten epipharyngis consists of three serrated spines, SI is plumose and the premandible has two indistinct teeth (Wiederholm, 1983).
Differential characteristics
H. maeaeri can be separated from the other Heterotrissocladius species by
a single mendial mentum tooth Heterotr mae mentum.