Several larval maxillary structures of previously unknown or confused homology were investigated in species and genera of the tribe Sabethini. Particularly important discoveries were made with regard to the maxillary brush, its structural homologs, and the development of an associated apical tooth-like process of the maxillary body. The specific determination of homologous structures of the larval maxilla explains the morphological similarities and differences exhibited by groups of seemingly related and unrelated taxa. The findings are of considerable use in understanding phylogenetic relationships and defining supraspecific categories. Structural relationships and homologies, and their significance, are discussed. Isostomyia Coquillett is elevated from a subgenus of Runchomyia Theobald to generic rank based on larval maxillary structure and correlated distinctions in the adult, larval, and pupal stages.