(Edwards, 1932)
Body
Small larvae up to 3,6 mm long (Cranston and Saether, 1982). Living larvae are greenish, bluish or purplish (Moller Pillot, 1984b). The L4 setae of the abdomen are short and simpel. The anterior and posterior parapods and procercus are present. Four anal tubules little more than half as long as the posterior parapods (Wiederholm, 1983).
Head
The head length is 0,315 - 0,346 mm (Cranston and Saether, 1982).
Antenna
The antenna consists of 4 segments. Lauterborn organs absent. The small third segment is unclearly separated from the second segment with a small apical coronet. The fourth segment is much longer than the third (Moller Pillot, 1984b) Acam antenna.
Mentum
The pale mentum is very characteristic in having three small teeth only. The dorsomentum consists of a plate with an outer row of 12 - 16 teeth. Beard absent (Cranston and Saether, 1982; Wiederholm, 1983; Moller Pillot, 1984b) Acam mentum.
Labrum
The pecten epipharyngis consists of three spines. SI is simpel, premandible with four teeth (Wiederholm, 1983).
Mandible
The mandible has a long distal tooth and four small teeth within. Seta interna is short with 4 - 5 simpel branches (Cranston and Saether, 1982; Wiederholm, 1983).
Differential characteristics
In the tribe Orthocladiinae there is no genus with a mentum resembling Acamptocladius. Also the dorsomental plates are unique Acam mentum. A. submontanus can be distinguished from A. reissi by the antenna with 4 segments. The 2nd and 3d segment are separated by a coronet. Third segment is longer than the 2nd Acam antenna.