Few data exist on invertebrate populations in farmland habitats of the Appalachian Mountains. However, invertebrate biomass and taxonomic composition may influence the potential for birds to reproduce. We collected invertebrates using sweepnets on 3 idle pastures and 3 idle hayfields in the Canaan Valley National Wildlife Refuge, WV. To evaluate the effects of mowing on invertebrate biomass, half of each field was mowed in August 1999 after grassland birds had finished nesting. In 2000, we collected terrestrial invertebrates on the mowed and non-mowed portions of each field. We documented 25 invertebrate families from 12 orders. Taxa in the orders Coleoptera (beetles), Diptera (flies), Homoptera (leafhoppers), and Orthoptera (grasshoppers and crickets) were the most abundant. Invertebrate biomass (g/150 passes of a sweep net) was similar (P = 0.763) between mowed (mean = 0.4302, SE = 0.0509) and unmowed (mean = 0.4704, SE = 0.0716) treatments. Biomass was similar between hayfields and pastures for each month (P > 0.05). We conclude that mowing did not influence the composition or biomass of our collections, which were comprised of invertebrate taxa from orders commonly consumed by breeding grassland birds.