Synopsis of the riffle beetle genus Zaitzevia (Coleoptera: Elmidae) in North America, with description of a new subgenus and species

Zaitzevia is represented in the Western Hemisphere by a rather variable species, Z. parvula which ranges from the Yukon of Canada southward to northernmost Mexico and from the Pacific coast eastward to the Black Hills of South Dakota and the Niobrara River of Nebraska. A new species from the Pacific Northwest, Z posthonia, is sufficiently different from all other known species of Zaitzevia to merit erection of a new subgenus, Suzevia. The most distinctive feature of Suzevia is the form of the penis, which is basally swollen rather than slender and cylindrical.