A POPULATION STUDY OF CULICOIDES-OBSOLETUS MEIGEN (DIPTERA, CERATOPOGONIDAE), AND OTHER CULICOIDES SPECIES IN THE FRASER VALLEY OF BRITISH-COLUMBIA

A seasonal light-trapping study of Culicoides species, in particular C. obsoletus Meigen, was conducted in the Fraser Valley of British Columbia to determine seasonal peaks and first and last appearance of these insects. Culicoides obsoletus is the causal agent of Culicoides Hypersensitivity (CH). an allergic dermatitis in horses, in British Columbia. Trapping at two sites in 1987 showed that C. obsoletus was first trapped in late March, and peaked in early May and again in late June. Small numbers were collected into mid-November. This coincided with the appearance and regression of clinical signs associated with CH in horses in the area. Stabling horses during the peak activity of Culicoides spp. has been recommended to prevent the development of CH. Light-trapping Culicoides both inside and outside stables showed that although fewer insects were caught inside, some (6%) were trapped indoors. A horse kept in an unscreened stable will not be protected from being bitten.