From the introduction:
"The subfamily Fanniinae is considered by present-day workers to include six genera, five of which are now known from North America. Fannia R.-D., the main genus, includes at the present time almost 200 known species. The other four contain only a few species, with one each in Platycoenosia Strobl and Piezura Rondani, three in Coelomyia Haliday, and seven in Euryomma Stein. In this revision, 46 species of Fannia, and one each of Euryomma and Piezura are described as new.
The present study is concerned with all the species of the subfamily that occur in the Nearctic region, which is here interpreted as extending throughout North America south to the limits of the Mexican Plateau. This southern limit is by no means sharply deﬁned, however, and the Mexican species generally show afﬁnities with Central and South American groups.
The number of correctly identified species previously known from the region is 45, of which 19 were known to be Holarctic. This paper brings the total to 105 by the inclusion of 48 new to science and another 12 new to the region. The North American species of the genus Fannia have been divided into 18 groups and subgroups, based largely on adult morphology (especially of the genitalic structures), but also, so far as was possible with limited data, on the immature stages as well. A tentative phylogeny has been postulated, and evolutionary trends outlined. Biological and distributional data have been compiled from the literature and from the material seen by the author."