The North and Central American Species of Isonychia (Ephemeroptera: Oligoneuriidae)

Kondratieff, Boris; Voshell, J

ABSTRACT: The species of the genus Isonychia Eaton (Oligoneuriidae) of North and Central America are revised, of which eighteen species are recognized, 3 (I. berneri, I. edmundsi, I. hoffmani) are described as new, and 11 species names (I. bicolor Walker = I. Christina Traver, I. circe Traver, I. fattigi Traver, I. harperi Traver, I. matilda Traver, I. pacoleta Traver, I. sadleri Traver; I. sicca (Walsh) = I. manca (Eaton); I. georgiae McDunnough = I. annulata Traver, I. thalia Traver; I. similis Traver = I. aurea Traver) are placed in synonymy. Isonychia campestris McDunnough is recognized as a full species. A Neotype is designated for I. arida (Say). Two subgenera, Isonychia s.s. and Prionoides Kondratieff and Voshell are recognized on the basis of adult and nymphal characteristics. Isonychia s.s. includes 4 species groups based on the male imago: bicolor group with 4 species (I. bicolor, I. rufa McDunnough, I. tusculanensis Berner, I. velma Needham), arida group with a single species (I. arida (Say) ), sicca group containing 5 species (I. berneri, I. campestris, I. edmundsi, I. intermedia (Eaton), /. sicca), and diversa group with a single species (I. diversa Traver). The subgenus Prionoides includes 7 species: I. georgiae, I. hoffmani, I. obscura Traver, I. sayi Burks, I. serrata Traver, I. similis. Isonychia notata Traver, known only from the holotype, is of uncertain status. A discussion of the nomenclatural history of the genus and each species is included. Many characters used in the past as specific criteria were found to be related to water temperature and geography