A revision of the family Dixidae, based on examination of museum specimens and reared specimens, is presented. Three genera and 42 species, of which the following 10 are new, are recognized: Dixa fluvica, D. melanderi, D. neohegemonica, D. pullogruma, D. repanda, Dixella aurora, D. cumbrica, D. deltoura, D. techana, and D. vespertina. All Nearctic species are described; illustrations of male and female terminalia are included. The genera Dixa Meigen, Dixella Dyar and Shannon, and Meringodixa Nowell are described; a key to the genera is included. The genus Dixapuella Dyar and Shannon is synonymized with Dixella Dyar and Shannon. Keys for adult males and females of the polytypic genera and 11 new synonyms are presented. A historical review of the Nearctic representatives of the family is included.
The external morphology of Dixella Indiana (Dyar), with illustrations, is presented. The morphology is compared briefly with other nematocerous Diptera.