(Uploaded by Plazi for the Bat Literature Project) I found Carios kelleyi Cooley & Kohls (formerly Ornithodoros kelleyi) (Acari: Ixodida: Argasidae) on Þve species of bats (Eptesicus fuscus, Myotis lucifugus, Myotis ciliolabrum, Myotis evotis, and Myotis volans) in the prairies of southeastern Alberta and north central Montana. This is the Þrst occurrence of ticks on bats in Canada. This is also the Þrst record of C. kelleyi on M. evotis and M. volans. Dates of parasitization ranged from 22 May to 17 October, and the number of ticks per host ranged from 1 to 44 (median two ticks per host). Number of parasitized individuals was signiÞcantly higher in rock-roosting E. fuscus compared with building-roosting E. fuscus, rock- and building-roosting M. lucifugus, and rock-roosting M. ciliolabrum and M. evotis. A signiÞcant sex bias was noted in rockroosting E. fuscus in 2000 with signiÞcantly more females parasitized. The number of ticks per bat host was highest in 2001, corresponding to the driest and hottest summer of the survey.