Medium-sized larvae, estimated 5-6 mm long. Colour not noted. Head capsule presumed oval; cephalic index not stated. Dorsally S5 anterolateral to DP, S8 and S7, S8 posteromediial to S7, anterolateral to DP; ventrally S10 posteromedian or posterior to S9, posterolateral to SSm; S9 and S10 anteromedial to VP, SSm medial or slightly posteromedial to S9.
Slightly shorter than mandible. Antennal ratio 4.6-5.2. Basal segment about 4.5x as long as basal width, with ring organ at about 0.65; segment 2 3-4x basal width; segments 3 and 4 subequal, slightly longer than peg sensilla. Style reaching middle of segment 3. Blade reaching at least segment 4. Accessory blade reaching apex of segment 2.
Slender, uniformly curved. Without any inner tooth; mola distally expanded to large, broad, protruding tooth with apically-directed, bluntly-rounded apex; seta subdentalis reaching to subapex of apical tooth. Ventrolateral seta undescribed.
Basal segment of palp about 3 x as long as wide, with ring organ at 0.3.
Saetheromyia was described for the Japanese species Psilotanypus tedoriprimus, later placed in Procladius. The body of the larvae reared to establish the pupal and adult identity, is undescribed and important features of the parapod claws and procerci are unknown. Clearly the genus is close to Procladius (Holotanypus), being differentiated by the ligula having outwardly-pointed inner teeth and the middle tooth large. Purported differences in the pecten hypopharyngis do not hold up.
Larvae of Saetheromyia live in slow-slowing rivers and streams with muddy bottoms in Fukushima, Kanagawa and Ishikawa Prefectures in Japan.