Characteristics of cephalic structures and spiracles of final-instar larvae of 65 species in 18 genera of the family Aphidiidae (Hymenoptera) are described and illustrated and keys are given for identification of genera and species. An additional seven species that were described and illustrated in an earlier paper (Mackauer and Finlayson 1967) are redescribed and included in the keys for a total of 72 species.On the basis of characteristics of final-instar larvae, taxonomic groupings of the family Aphidiidae mainly conform to those based on characteristics of adults, with the following exceptions.Within the tribe Aphidiini the genus Calaphidius appears to belong in a new subtribe because of the unusual form of the pleurostoma, and the presence of numerous small sensoria in the maxillary and labial palpi, and of an atrium in the prothoracic spiracle which is absent in all other species of this tribe.It is suggested that the tribe Trioxini (Aphidiinae) should be a separate subfamily, the Trioxinae, because of the presence of a hypostomal spur which was not found in any of the other aphidiids examined. Within this suggested new subfamily the genus Lipolexis appears to be the most primitive form examined because, in addition to a hypostomal spur, it has a complete epistoma which is lacking in all other aphidiids examined; it is suggested that this genus be placed in a separate tribe, the Lipolexini. The trioxines appear to be the most primitive of the Aphidiidae and form a bridge between the Braconidae and the Aphidiidae.The Aphidiini (Aphidiinae) appear to be at the peak of the evolutionary scale of the Aphidiidae because of the loss or reduction of the pleurostomal–hypostomal sclerite, making the identities of the pleurostoma and hypostoma less distinguishable.