Bumble bees (Bombus spp.) are vitally important pollinators of wild and managed flowering plants. In the contiguous United States 30 species of bumble bee are found west of the Rocky Mountains. Compared to the 20,000 described species of bees, bumble bees possess relatively long tongues. However, within the bumble bee genus, tongue length varies across species. The length of a bumble bee’s tongue is indicative of the types of flowers they forage on for nectar and pollen. Bumble bees with relatively short tongues may be found foraging on flowers with short corollas, while bumble bees with long tongues may be found on flowers with long corollas. Yet others, like the western bumble bee, are known to rob nectar from flowers by biting holes at the base of the corolla, thereby bypassing the flower’s reproductive system.
While bumble bees vary dramatically in body size and color, several co-located species have convergent color banding patterns. These serial mimics can make it difficult to identify a bumble bee to species. Thus, learning to diagnose facial characteristics like cheek length, as well as ‘hair’ color patterns on the head, thorax, and abdomen are necessary. To assist you in the identification of western bumble bees, please refer to our published field guide Bumble Bees of the Western United States, available here at http://pollinator.org/books/htm and http://www.fs.fed.us/ wildflowers/pollinators/animals/bees.shtml.
This guide provides valuable information on the geographic distribution and likelihood of detecting bumble bees throughout the year. Utilizing the taxonomic key, body diagrams, and photographs of bumble bees in the wild will help users determine the bumble bee species in their community. Unfortunately, some bumble bees are in decline, and one species is thought to be extinct. Thus, possessing the ability to identify bumble bees to species in your community will help conservation biologists track the status of bumble bee communities across the United States.