The Appalachian Mountains contain some of the highest millipede diversity on the planet, including many endemic and range-restricted species. Millipedes have extremely low dispersal capacity, strict environmental requirements for survival and, in the case of the family Xystodesmidae, are completely blind. Coupled with the complex topology of the Appalachians, xystodesmid millipedes have speciated in the eastern United States to a greater degree than in any other region. Many of the taxonomic relationships within the Xystodesmidae remain to be tested using modern molecular techniques, and numerous species await description. The subtribe Nannariina, for example, contains 3 genera and 19 species, yet evidence suggests the tribe may actually contain over 100 species. Traditional taxonomic work has been hindered by a paucity of researchers in the field, and a necessary reliance on morphological characters for species delimitation. The external male genitalia, known as gonopods, are the structures which have most often been used to define species boundaries. However, in many groups, including the Xystodesmidae, the gonopods are extremely simple, making it difficult to discern whether similarity between gonopods is a result of shared ancestry or morphological convergence. Further complicating matters, somatic characters are often uniform between species, and some obvious phenotypes, such as color pattern and hue, are shared between genera in aposematic mimicry rings. Leading to the formation of mimicry rings between distantly related genera, their bright coloration functions to advertise a cyanide-based defense. Some species have been recorded as having six color patterns, each a member of a different mimicry rings. The factors which drive some taxa to participate in mimicry rings, while others have a myriad of hues and patterns, unmatched by other species, are unknown. Here I investigate the phylogenetic relationships between the tribes and genera of the Xystodesmidae, with the aims of (1) understanding the role of homoplasy within the Xystodesmidae, (2) delineating tribal and generic boundaries within the family, (3) describing species in the genus Nannaria for the purposes of revising the subtribe Nannariina, and (4) investigating mimicry and color variability through a detailed color atlas for North American Xystodesmidae. I found that 95% of the morphological characters traditionally used in xystodesmid taxonomy are homoplasious (HI > 0.5), delineated the Apheloriini, Appalachioria and Sigmoria, described 34 new Nannaria species, and created a color and mimicry dataset of 956 Xystodesmidae for use in future studies of color variability. / PHD / Millipedes are soil dwelling animals that eat leaves, decaying wood and, sometimes, fungi. They are typically found beneath dead leaves in damp forests. The Appalachian Mountains are home to an incredible number and variety of millipede species. This is partly due to the age of the Appalachians, which are around 10 – 20 million years old, its rugged terrain, and the fact that the complexity of the terrain acted as a refuge for many different animals during the last ice age. However, millipede behavior also played a role in their diversification. Most millipedes are relatively slow moving, and many are blind. Millipedes also dry out easily, and therefore need to live in very wet habitats. All of these factors led to populations of millipedes becoming isolated in gullies and on mountains throughout the Appalachians. Over time, these populations became distinct species, many of which are still unknown to the scientific world. One group of millipedes in the family Xystodesmidae, the Nannariina, have only 19 known species; however, evidence suggests that the group may contain over 100 undescribed species. There are several reasons that groups such as the Nannariina have so many undescribed species, there are very few people studying them, they live in hard-to-reach areas, they are not pests, invasive, or have immediate economic importance. However, one of the biggest reasons is that traditional descriptions of millipede species rely on physical characters that often are not informative about relatedness (as an example stating that all green-eyed people are closest relatives). Making matters more complex, many unrelated species in the family Xystodesmidae have the same color. There are even millipede species that have six color patterns in one species. We do not know why some millipede species are a single color and others are very colorful. Here I study the evolutionary relationships between members of the Xystodesmidae, with the aims of (1) investigating anatomical convergence within the Xystodesmidae, (2) defining evolutionary groups within the family, (3) describing species in the genus Nannaria, and (4) investigating mimicry and color variability through a detailed color atlas for North American Xystodesmidae.