Published online by Cambridge University Press: 31 May 2012
Centroptilum infrequens McDunnough, 1924 was found to be widespread in Canada and was described in detail at the 5th International Ephemeroptera Conference, Marysville, Australia, 1987 (Lowen and Flannagan 1989). At that time, similarities between C. infrequens and published accounts of Pseudocentroptilum pennulatum (Eaton 1870) were noted and it was suggested that these species are conspecific. We have recently compared specimens of C. infrequens with specimens of P. pennulatum from western Europe, and have noted no discernable differences at any life stage. We therefore conclude that Centroptilum infrequens McDumough, 1924 is a junior synonym of Pseudocentroptilum pennulatum (Eaton) 1870. This is the first record of Pseudocentroptilum in North America and the first record of a holarctic Pseudocentroptilum species, as P. pennulatum is also known from the arctic Ural and Pacific Coast regions of the Soviet Union.