Descriptions are provided for the pupae and larvae of the following species: Tanytarsus bathophilus Kieffer, T dibranchius Kieffer in Zavrel, T. ejuncidus (Walker), T. eminulus (Walker), T. gregarius Kieffer, T. inaequalis Goetghebuer, T. lestagei Goetghebuer, T. lugens Kieffer, T. medius Reiss & Fittkau, T. mendax Kieffer, T. occultus Brundin, T. pseudolestagei Shilova, T striatulus Lindeberg, T telmaticus Lindeberg, and T. volgensis Miseiko. Descriptions of pupae are given for Tanytarsus aberrans Lindeberg, T. aculeatus Brundin, T latiforceps Edwards & Thienemann, T. longitarsis Kieffer, T. multipunctatus Brundin, T. smolandicus Brundin, and T. tika (Tourenq). Diagnoses of both immature stages are provided for Tanytarsus dispar Lindeberg, T. formosanus Kieffer and T. mancospinosus Ekrem et al. Tanytarsus decipiens Lindeberg and T. palmeni Lindeberg are new junior synonyms of T. lestagei. Tanytarsus socialis Lindeberg and T. simulans Lindeberg are new junior synonyms of T. telmaticus. Tanytarsus profundorum Kieffer is a new junior synonym of T. inaequalis. Tanytarsus verticillatus is a new junior synonym of T. bathophilus. Tanytarsus fimbriatus Reiss & Fittkau is a new junior synonym of T. volgensis. Tanytarsus latiforceps Tokunaga, 1964: 619, is a junior homonym of T. latiforceps Edwards and is given the new replacement name Tanytarsus tokunagai. Tanytarsus pseudotenellutus Goetghebuer is transferred to the genus Paratanytarsus. Diagnostic characters are given for the adult males of species with new synonymies or those which previously had unclear diagnoses. Keys to pupae and larvae are included.
