Uncovering the evolutionary and ecological process that has lead to biodiversity has been, and continues to be one of the most fascinating aspects of biology. One way to assess such processes is to study the diversity and limits of species. One group of interest in biodiversity are the crane flies (Diptera: Tipuloidea) because of their extreme diversity (>15,000 described species, representing 10% of all Diptera). Little is known about the patterns and processes responsible for creating such species diversity in crane flies. Often termed the fundamental units of life, species remain a difficult entity to define. Through recent innovations in analytical techniques and theoretical underpinnings, the process of delimiting species has resurged in interest. These new procedures have opened the door to define species like never before. Before defining the limits of species, a monophyletic group of species must be accurately described so as to include the most relevant species. I defined a new genus based on unique aspects of the male genitalia in a group of crane flies (Diptera: Tipuloidea). Based on key morphological features, 15 species were placed within the new genus, Neophylidorea. A preliminary revision of the group indicated that the diversity was perhaps over-estimated. I used four criteria and a variety of multivariate methods to delimit species of Neophylidorea. Based on the criteria used including morphology, geometric morphometrics, molecular sequences and ecological niche divergence, the four morphospecies built from the preliminary revision represent distinct, independently evolving lineages. A formal revision of these four species, and two additional species that lacked data sufficient to perform detailed analyses, concludes this dissertation. One of the two species lacking data is a newly described species to science.