Richard K. Allen

Geographic Distribution and Reclassification of the Subfamily Ephemerellinae (Ephemeroptera: Ephemerellidae)

The geographic distributions of the genera are included on maps and 9 latitudinal distributional zones are established, revising the system proposed by Allen and Brusca. The genera are included in 2 tribes, Ephemerellini and Hyrtanellini n. tribe, and Acerella, Attenella, Caudatella, Cincticostella, Crinitella, Dannella, Drunella, Ephemerella s.s., Eurylophella, Hyrtanella, Serratella, Teloganopsis, Timpanoga andTorleya are treated as genera. Drunella is composed of five subgenera: s.s., Eatonella Myllonella n. subgen., Tribrocohella n. subgen., and Unirhachella n. subgen.; Cincticostella of 3: s.s.,Rhionella n. subgen., and Vietnamella New Combination; andDannella of 2: s.s. and Dentatella n. subgen.

The Distribution of Southwest North American Mayfly Genera (Ephemeroptera) in the Mexican Transition Zone

Halffter (1976), in an attempt to explain the origin and dispersal of Neotropical insects in North America, developed a theory of reference models, with which the distribution of a given group can be compared. He characterized dispersal in the Mexican Transition Zone (the southern U.S., Mexico and most of Central America), and grouped patterns by origin as follows: the boreal Paleo-american and Nearctic Patterns, and the austral Ancient South American and Typical Neotropical Patterns, and stated that some groups fit these patterns poorly or not at all. Southwest genera are ideal subjects to test the fit of mayflies to these models, and it is concluded that they fit three of the four models very well. Genera of recent boreal origin do not fit the Nearctic Pattern criteria, except for three species, but fit their own unique pattern with their own criteria. Those that fit the Paleo-american Pattern have disjunct distributions in Meso-america and North America north of Mexico; those that fit the Ancient South American Pattern have a nearly equal number of species in South America, Mesoamerica and North America; and those that fit the Typical Neotropical Pattern have more species in South America, fewer in Mesoamerica and still fewer in North America.

Distribution Patterns of North and Central American Mayflies (Ephemeroptera)

Collection records of North and Central American mayflies were plotted on maps, based on published records, and the distributional limits of species were found to form 24 distinct distribution patterns within 5 larger subdivisions. The Arctic subdivision includes 15 species that occur only above 58° north, and includes two patterns, the Palearctic (Europe) and the Nearctic (North America). The North American subdivision includes 14 species in two patterns that occur almost from coast to coast. The Western North American Subdivision includes 209 species in 9 patterns whose distributional limits are west of the east slope of the MacKenzie, Rocky, and Sierra Madre Occidental Mountains to Jalisco (21°N). The Eastern North American Subdivision includes 373 species in 10 patterns east of the western mountains to Veracruz (21°N). The Mesoamerican Subdivision includes 99 species in 2 patterns, and the distributional limits of most species are from Panama to Jalisco and Veracruz, Mexico. Species occur in only one pattern and one subdivision, except for those that are widely distributed or holarctic, and patterns are composed of only boreal species, or of boreal and austral species, but none are composed solely of austral species.