(Kieffer, 1918)
Body
Large larvae with a length up to 12 mm. Living larvae are greenish. The fringe of swimming hairs is present (Moller Pillot, 1984a).
Head
The head is relatively small compared to the body, has a length of 0.55 - 0.65 mm with a cephalic index of 90 - 100% Tan head (Moller Pillot, 1984a).
Antenna
The antennal segments are all yellow and the antennal ratio is 5 - 6. The ring organ is situated at 0.8 - 0.9 of the height of the first segment. The second segment is normal and lacks a tuning fork (Wiederholm, 1983; Moller Pillot, 1984a).
Mentum
Dorsomentum with 5 - 6 teeth on each side. Both parts are broadly joined in the middle (Moller Pillot, 1984a)
Ligula and paraligula
Ligula with 5 equal-sized yellow teeth in a straight line or slightly convex. Paraligula fan-like with with appr. 10 hair-like rays, resembling the paraligula of T. punctipennis Tan punctipennis ligula.
Mandible
The mandible is very characteristic. The distal part of the inner margin with 2 long flat teeth and 2 small pointed accessory teeth next to each other. The basal tooth is a hump which is folded inwards distally Tan kraatzi mandible.
Maxilla
The maxilla is short with an undivided basal segment.
Anal tubules
4 anal tubules which are longer than wide Tan 4 anal tubules.
Posterior parapods
Some of the smaller claws have a broad base and they lack additional spines Tan vilipennis claws.
Differential characteristics
The yellow ligula with 5 equal teeth Tan punctipennis ligula, the cephalic index (90 - 100%) and the shape of the mandible Tan kraatzi mandible are distinctive for the genus Tanypus. T. vilipennis differs from the other species by having only 4 anal tubules Tan 4 anal tubules instead of 6 Tan 6 anal tubules.