This report is a synopsis of the terrestrial arthropod faunas collected from four peatlands in southern Ontario. The peatlands surveyed were the Wylde Lake bog (43°55′N, 80°30′W), Crieff fen (43°25′N, 80°07′W), Oliver bog (43°20′N, 80°16′W), and the Wainfleet bog (42°55′N, 79°17′W). Arthropods were collected in yellow pan traps (aluminum pan traps at Wainfleet) during the period May 1987 to June 1988 (including the period of snow cover from December to March). A total of 33 029 specimens were removed from the pan trap samples and of these 17 173 individuals were assigned to species. Between 603 and 870 species of arthropods were identified from each site. Collections from each site were compared using taxonomic and ecological groupings (based on feeding behaviour and habitat preference) of species. Sorensen's Index of Similarity was used to compare the overlap of species among sites. The Hymenoptera, Diptera, Coleoptera, and Araneae were the most species-rich orders collected at each site. More species preferring peatlands were collected at each of the three undisturbed peatlands (Wylde L., Crieff, and Oliver) than at the mined bog, Wainfleet. Species not usually associated with peatlands were more numerous in the Wainfleet collection than in collections from the undisturbed sites. It is concluded that grouping of species by habitat preference is a useful technique for assessing habitat disturbance.