Half of the bumblebee species in eastern North America are in decline. This trend holds true in southern Ontario, where seven of the 14 bumblebee species found in surveys from 1971 – 1973 were found to be either absent or in decline when surveyed 30 years later. Some of these, like the rusty-patched, the gypsy cuckoo and the American bumblebee, were once common and/or widespread in parts of the province. The causes of decline are not fully understood, though it is widely accepted that habitat destruction and the use of pesticides are significant threats.
The rusty-patched bumblebee was once common and widespread in eastern North America, including southern Ontario. This species has declined dramatically since the 1970s and is now listed as endangered in Canada. Only a few specimens have been sighted in Ontario in recent years. Though the causes of decline are poorly understood, threats include habitat loss, exposure to pesticides and pathogens from non-native bumblebees used in greenhouses.
This large bumblebee once had an extensive range in Canada and was recorded in all provinces and territories except Nunavut. There has been a large decline in the past 20 – 30 years, and in 2014 the species was listed as endangered in Canada. It has not been found in Canada in recent years, and the last recorded sighting in Ontario dates back to 2008. The gypsy cuckoo bumblebee is a nest parasite of other bumblebees, including two species that are also in decline. Primary threats include the decline of these other “host” bumblebees, as well as pesticide use (particularly neonicotinoids) and pathogens from non-native bumblebees used in commercial greenhouses.
This above ground-nesting bumblebee is one of the most rapidly declining species in eastern North America. Studies in the U.S. show a significant range reduction and decline in abundance in recent years, even where it was once common. The American bumblebee inhabits open fields and grasslands, and is still found in a few sites in southern Ontario. In surveys performed near Guelph from 2004 – 2006, however, the species was completely absent, even though it had been documented in the region 30 years earlier.
Sheila Colla et al. (2012). Biodiversity and Conservation, 21 (14): 3585-3595