DescriptionComparative black fly taxonomy has largely been limited in scope to comparisons within a continent, or at most by hemisphere. This gap in black fly systematics has been aided by barriers of language, geography, and specimen availability. This thesis provides a morphological comparison of 19 of the 26 known world genera of black flies, along with a new genus, Adlerella, which is described herein. This genus is also supported by molecular data. A morphology based phylogeny was generated, providing evidence for a Holarctic origin for the family Simuliidae. The somewhat aberrant genus Crozetia’s basal relationship to the other Simuliini suggests a possible black fly relict. This study includes the first combined molecular and morphological based phylogeny of the world Simuliidae genera from all of Wallace’s biogeographic regions, minus seven of the known genera. The first analysis of paralogous genes in the Simuliidae is also performed. A new alignment for the 12S and 28S nucleotide sequences is proposed based on manual secondary structural alignment. Strong branch support and congruence between molecular and morphological data confirm the subfamiliy and tribe divisions of the Simuliidae. Due to particularly strong branch support for the tribe Prosimuliini, it is raised to the subfamily Prosimuliinae, and a new combination for the subfamily Simuliinae is proposed. This thesis also includes a comprehensive analysis of simuliid species tolerance values based on chromosomal identifications. Pollution tolerance values are reported for the 39 species of black flies known in New Jersey. Species of the same genus exhibited high variation in tolerance values, questioning the accuracy of generic-level tolerance values for the Simuliidae. An index for predicting the occurrence and proliferation of the Simulium jenningsi group, which includes the major pest species of Simuliidae in the eastern United States, is proposed, with implications for control programs worldwide.