a1 Department of Biology, Bishop's University, Lennoxville, Quebec
a2 Entomology Research Institute, Central Experimental Farm, Ottawa, Ontario
The attraction of large numbers of the ornithophilic black fly, Simulium euryadminiculum Davies, to its host, the common loon, Gavia immer (Brünnich), to the place where the loon skin had been washed, and to a dried museum skin of the loon, is described. The fly was not attracted to museum skins of a pied-billed grebe, common merganser and herring gull. The data suggest a system of olfaction in host location, probably involving volatile, air-borne substances. It is possible that the colour or pattern on the head and neck of the loon serves to attract the fly to this area of the host.
(Received January 24 1964)