Arlea judithnajtae n. sp. (Collembola: Isotomidae), a temperate North American member of a Gondwanan genus

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.