Bat flies represent an ectoparasitic group of insects that have largely been overlooked in the study of insect vision. It is assumed that increasing sedentariness in ectoparasites spurs certain reductive trends concerning wing and eye morphology. While other ectoparasitic groups (e.g. fleas and lice) seem to have converged on a general theme of eye- and winglessness, bat flies exhibit a unique variation in these two features. We will explore the general evolutionary patterns of eye and wing modification of bat flies in the light of their phylogeny. Additionally we will provide the first molecular characterization of long-wavelength opsins from this group and explore rates of evolution and selection in a phylogenetic context. This will give insight into general evolutionary trends related to the phenomenon of hexapod ectoparasitism and their visual acuity.