Intensive collecting for the All-Taxa Biodiversity Inventory in Great Smoky Mountains National Park, United States, yielded many specimens of Arlea judithnajtae n. sp. (Collembola: Isotomidae). This new species differs from other species of Arlea Womersley, 1939 in having a combination of smooth setae, seven large sensilla on Ant. IV, dorsal sensilla of Th. II-III and Abd. I-III in middle setal rows and inconspicuous sensilla on Abd. V. It is most similar to A. psammophila Mendonça, Abrantes & Fernandes, 2006 but that species has eight or nine Ant. IV sensilla and has the dorsal thoracic and abdominal sensilla in the posterior row of setae. A key is provided for separation of known Arlea species. Arlea judithnajtae n. sp. is the first member of its genus reported from a non-Gondwanan continent (North America), suggesting that the southern Appalachian region of North America has been a refugium for otherwise extinct taxa. Alternatively, it may have been previously overlooked due to its small size and close resemblance to other white, eyeless isotomids.
Biogeography, identification key, Nearctic, refugium, new species.