Reference to the National Insect Collection at Ottawa shows that species of the genus Cuterebra have been collected in various localities of Western Canada at different times. Of these Cuterebra grisea Coq. is distributed throughout Manitoba, Saskatchewan, Alberta, North-West Territories and British Columbia. There is one record each of C. emasculator Fitch (determined by Aldrich as C. fontinella Clark), of which the locality is unknown, and of C. fasciata Swenk, from Peachland, British Columbia. The specimen of C. emasculator bears a note that it had been reared from a chipmunk, Tamias striatus lysteri Richardson. The remaining species, C. americana var. polita Coq., C. similis Johnson and C. tenebrosa Coq. have all been collected in British Columbia. There is but a single record from the Eastern Provinces and that a specimen of C. fasciata from Bathurst, New Brunswick, dated August, 1900. Altogether there are 22 specimens in the National Collection belonging to six species. Of these there are 11 specimens of C. grisea, which would thus appear to be the most prevalent species in Western Canada. The comparative paucity of specimens may be correctly attributed to the peculiarly shy habits of the species, the adults of which, according to information furnished me by Criddle, prefer rather dark situations, such as outbuildings, summer kitchens and the ground burrows of rodents. They occur on the wing from June to September and are probably to be found closely attendant upon the haunts of their rodent hosts. That the percentage of parasitism is not high is concluded from the fact that Parker and Wells (1919), in a careful examination of over a thousand rodents in Montana for possible infestation by the Rocky Mountain spotted fever tick, Dermacentor venustus Banks, found but two that were parasitised, each with one larva of C. tenebrosa.