Bombus vosnesenskii, the distinctively-patterned Yellow-faced Bumble Bee, has undergone a significant and rapid range extension in British Columbia. Known initially from a single record of a few specimens at Osoyoos in 1951, it was put forward in 1996 as a species that warranted a threatened or endangered status because of its severely restricted range in the province. However, since 2000, the species has expanded north in the Okanagan Valley, west to the Similkameen Valley and, especially, has become firmly established in south coastal regions of the province, including Vancouver Island. Population increases in B. vosnesenskii to the south of BC have also been reported. The reasons for the rapid expansion of B. vosnesenskii in BC are unclear. Particularly in lowland southwestern BC, the range expansion might have been enhanced through escapes from colonies kept as pollinators of agricultural crops. The spread of B. vosnesenskii has coincided with the decline of B. occidentalis, so the former may have been introduced or naturally expanded its range at the same time as a niche was becoming vacant
