NEW ADDITIONS TO THE INVENTORY OF COLORADO MAYFLIES (EPHEMEROPTERA)

Four mayfly species, Baetis dardanus, Paracloeodes minutus, Homoeoneur ia alleni and Rhithrogena pellucida are reported from Colorado for the first time. Homoeoneuria and Paracloeodes represent new generic recor ds for the state. The male terminalia of R. pellucida from Colorado an d a paratype from Minnesota are illustrated and compared, and characte rs are given to separate this species from the four other Rhithrogena species in Colorado. Previous tentative records for two additional spe cies, Baetis virile, and Leptophlebia nebulosa are confirmed. Biogeogr aphic affinities for several species in the North Platte River system are discussed. A total of 43 genera and 101 species of mayflies are no w known from Colorado.