A REVISION OF THE GENUS CAENIS IN NORTH-AMERICA (EPHEMEROPTERA,CAENIDAE)

The North American species of the genus Caenis are revised, and illustrated keys to larvae and adults presented. Eleven nominal species, including one new species, are recognized. Based on shared morphological and behavioral characters in the larvae, adults, and eggs, these species are grouped as follows: diminuta group - C. amica Hagen, C. candida Harper and harper, C. diminuta Walker, C. latipennis Banks, C. punctata McDunnough, and C. youngi Roemhild; hilaris group - C. anceps Traver, C. hilaris Say, C. macafferti n. sp., and C. tardata McDunnough. Caenis bajaensis Allen and Murvosh appears to have been independently derived and is not placed in either group. For each nominal species, synonymies, larval and adult descriptions, figures, and a discussion of taxonomy, distribution, and biology and ecology, are included. Newly discovered synonyms are: C. amica Hagen = C. simulans McDunnough n. syn.; C. latipennis Banks = C. forcipata McDunnough n. syn., C. jocosa McDunnough n. syn., C. delicata Traver n. syn., C. gigas Burks n. syn.