Predaceous water beetles (Coleoptera: Adephaga : Dytiscidae, Gyrinidae) collected along the Horton and Thelon Rivers in the Arctic Central Barrens of Canada

Predaceous water beetles were collected during expeditions along two northern Canadian rivers during 2000 and 2002. Twelve species of Dytiscidae (including 11 named species and one additional genus identified from a larva) and one species of Gyrinidae are recorded from 20 sites along the Horton and Thelon rivers in the Central Barrens area of the Canadian Arctic. These records represent an extension of the distributions of four species to the northeast in the Northwest Territories (NWT), and two species to the northwest in Nunavut (NU). Oreodytes sanmorkii is reported for NWT and for the mainland of NU for the first time. Ilybius erichsoni, Hydroporus geniculatus, and Gyrinus opacus are reported for NU for the first time. Five species were recorded for the first time from the Southern Arctic ecozone, and one from the Taiga Shield ecozone. The majority of specimens were collected in habitats that were consistent with those previously known for each species.