Abstract: Flightless species of darkling beetles Coleoptera: Tenebrionidae and Zopheridae of the Appalachian region belong to the genera Ammodonus, Blapstinus, Eutochia, Helops, Meracantha, Opatrinus, Paratenetus, Phellopsis and Polypleurus. Collection records and field observations show that Appalachian "microdeserts" - the dry sandy deposits, shale barrens, and rock outcrops - are isolated habitats for a few odd species that appear to have disjunct populations and unexpected range extensions in the region. This study reviews the known distribution of these insects and their sister taxa, recognizes some distinct species assemblages, and hypothesizes the origins of present distribution patterns. Some beetles having typically southern and coastal plain distributions show inland range extensions in the Appalachian ridges, while boreal species range southward in the higher elevations, making the region a unique area of overlap for northern and southern faunal elements. Psammophiles and other xeric-adapted species in the Appalachians and surrounding northern areas are evidently relicts of the postglacial Hypsithermal Interval.