Species treatment for Oligonicella scudderi completed. Excerpt: Several recent authors have listed two different species as belonging to Oligonicella within the fauna of the United States, O. scudderi and O. bolliana. Initially, between 1872-1930, when the genus architecture was in flux between Oligonyx and Oligonicella, this grouping contained four separate taxa from this region: O. scudderi, O. bolliana, O. missouriensis, and O. uhleri. The original designations of these species were separated by variable characteristics of body/leg length and wing pigmentation. Scudder was first to cast doubt on the demarcation of these taxa in 1896. After comparing an O. scudderi specimen that was collected from “Carolina” to O. bolliana material that was collected in Texas, Scudder remarked, “I am therefore inclined to believe these two supposed species to be identical”. Rehn & Hebard subsequently synonymized O. uhleri with O. scudderi in 1916, noting that “none of these characters are of sufficient importance in this insect to be considered of specific value.” They noted within this same paper that Saussure & Zehntner’s establishment of O. bolliana in 1894 should be regarded as a subspecies of O. scudderi “if sufficiently distinct to warrant racial separation.” In 1931, Hebard synonymized the remaining species with O. scudderi, stating, “It is now evident that missouriensis represents the same insect and that the more pallid western specimens for which we have thought bollianus might be used in a racial sense do not show sufficient or constant enough differences to warrant nominal recognition of any kind.” Thus, according to Hebard’s extensive analysis of Oligonicella material from the United States, the four original taxa that were initially separated by variable characters all represent variations of the same species, Oligonicella scudderi. Despite this synonymization, O. bolliana has somehow persisted in the literature as being valid while the equation of O. missouriensis has been accepted, even though both were dispatched in the same paper and with the same rationale. There has been no literary justification as to why one of these synonymizations has been accepted and the other has not, leading to the conclusion that the continual listing of O. bolliana as a valid species has been merely a matter of oversight. Furthermore, there has been no recent analysis of any Oligonicella type material or collected series that suggests that more than one species is involved. With this clarification, it is hereby established that O. bolliana should continue to be regarded as a synonym of O. scudderi, therefore leaving but one species of Oligonicella within the region of the United States.