This paper is a study on the taxonomy of the immature stages of the Syrphidae. Special attention has been paid to the groups of the family which do not have aphidophagous larvae. The external morphology of a typical saprophagous larva and comparative chaetotaxy of the larvae is described and new sensilla are recorded. The changes in appearance at puparium formation: are described. The external features of the third instar larvae and puparia of forty-six species are described and notes on their biology are included. A key for the identification of these and some other larvae is given. A major revision of the classification of the family is proposed as a result of the study of the larvae. This recognizes only two subfamilies, Syrphinae and Milesiinae. Most of the present subfamilies are reduced to tribal status but the Cheilosiinae prove to be heterogenous and its species fall into other groups.