Diacyclops languidoides (Lilljeborg, 1901) s.l. and Acanthocyclops montana, new species (Copepoda, Cyclopoida), from groundwater in Montana, USA

Species of cyclopoid copepods collected from wells on the floodplains of the Flathead and Whitefish Rivers, State of Montana, USA included Diacyclops languidoides s.l. and Acanthocyclops montana , new species. New records of D. languidoides , recorded for the first time from the USA, are also given from Colorado and Saskatchewan. The first complete description of a North American member of the D. languidoides species-complex is furnished. A. montana most resembles A. phreaticus , but differs in proportions of the caudal setae, terminal spines of leg 4 endopodite 3, and details of the seminal receptacle.