US Geological Survey


Date of this Version



Published in THE PRAIRIE NATURALIST 36(1): March 2004 Published by the North Dakota Natural Science Society.


Graphoderus liberus is a moderate sized (11 to 12 mm) predaceous diving beetle (Coleoptera: Dytiscidae). Two species of Graphoderus have been recorded in North Dakota, G. perplexus, and G. occidentalis (Gordon and Post 1965, Hanson and Swanson 1989). Graphoderus liberus is transcontinental from New York to British Columbia, but it is more common along the coasts (Larson 1975). In Canada, G. liberus is uncommon; in Alberta only two specimens have been reported from woodland pools (Larson 1975). There have been no records of G. liberus occurring in North Dakota. Graphoderus liberus is easily distinguished from G. perplexus and G. occidentalis by the lack of anterior and posterior dark transverse bands on the pronotum (Fig. I). April 17,2000, we collected one male G. liberus at the Cottonwood Lake Study Area (Swanson 1987), Stutsman County, North Dakota. The specimen is archived in the aquatic invertebrate collection at the U. S. Geological Survey's Northern Prairie Wildlife Research Center in Jamestown, North Dakota. We captured the specimen in a funnel trap (Swanson 1978) set in 64 cm deep water in the shallow marsh zone (open water phase) of a seasonal wetland (Stewart and Kantrud 1971).