Platypezidae occupy an important basal position within the Muscomorpha. However, morphological analyses of larval Platypezidae are incomplete and early stage data is insufficient to inform phylogenetic analysis and recognition of groundplan characters and states within Muscomorpha. For example, knowledge is poor of the characters of respiratory organs, head, head skeleton, thorax and segmental sensilla. In this study we describe and compare these features of 16 species in 11 genera. The head appears as a distinct fleshy organ with atrium and antennae and maxillary organs separated on the dorsal surface. Head skeletons are characterised by an anteriorly projecting labrum and labium with laterally placed mandibles. The prothorax is frequently armoured with sclerotised regions and spicules. A repeated and uniform pattern of up to 11 pairs of sensilla circumvent each thoracic and abdominal segment. Respiratory organs vary little in size and arrangement of spiracular openings. Using a set of 43 larval and puparial characters and based on a Brachyceran outgroup, a sequence of genera is established which places Melanderomyia as the most basal. These results are compared with estimates of phylogeny based on adult characters.