Insecta, Ephemeroptera: transcontinental range extensions in western North America

Among the 631 valid species of Ephemeroptera (mayflies) that are presently known from North America (McCafferty 2007), relatively few have been known as having more or less continuous (non disjunct) transcontinental distribution patterns from the east coastal provinces of Canada and or east coastal states of the USA to the west coastal provinces of Canada or the west coastal states of the USA or Mexico. The best representation of such distribution patterns is in the family Baetidae, e.g., Acentrella turbida (McDunnough), Baetis bundyae Lehmkuhl (relatively sparse and northern), B. flavistriga McDunnough, B. tricaudatus Dodds, Callibaetis ferrugineus (Walsh), C. fluctuans (Walsh), Diphetor hageni (Eaton), Paracloeodes minutus (Daggy), Procloeon bellum (McDunnough) (relatively sparse and northern), and P. pennulatum (Eaton) (relatively sparse and northern). In other mayfly families such continuous transcontinental patterns are uncommon among species, or in the case of Caenidae, less common. They include such species as Ameletus subnotatus Eaton (northern) (Ameletidae); Baetisca lacustris McDunnough (Baetiscidae); Caenis amica Hagen, C. latipennis Banks, and C. tardata McDunnough (Caenidae); Ephemerella aurivillii (Bengtsson) and E. excrucians Walsh (Ephemerellidae); Ephemera simulans Walker and Hexagenia limbata (Serville) (Ephemeridae); Heptagenia pulla (Clemens) and Maccaffertium terminatum (Walsh) (Heptageniidae); Tricorythodes minutus Traver (eastern records possibly incorrect) (Leptohyphidae); Leptophlebia cupida (Say), L. nebulosa (Walker) and Paraleptophlebia debilis (Walker) (Leptophlebiidae); Metretopus borealis (Eaton) (relatively sparse and northern) (Metretopodidae); Ephoron album (Say) (Polymitarcyidae); and Siphlonurus alternatus (Say) (northern) (Siphlonuridae). In addition to these transcontinental species, there are a few others that are disjunct East and West species that are absent to a considerable extent in central regions of the continent.