KEY: Vulnerable, at moderate risk of extinction because of restricted range, relatively rare populations (often 80 or fewer), recent and widespread declines, or other factors; data deficient, inadequate information for assessment of risk category because of a lack of information about population size or about threats to the population or because of taxonomic uncertainty about the validity of the taxon; critically imperiled, at high risk of extinction because of extreme rarity of populations (often 5 or fewer), steep declines, or other factors; possibly extinct, missing or known only from historical occurrences but with some hope of rediscovery; imperiled, at high risk of extinction because of highly restricted range, rare populations (often 20 or fewer), steep declines, or other factors.
SOURCE: Adapted from Shepherd, M.D., D.M. Vaughan, and S.H. Black (Eds). Red List of Pollinator Insects of North America. CD-ROM Version 1 (May 2005). Xerces Society for Invertebrate Conservation, Portland, Oregon, http://www.xerces.org/Pollinator_Red_List/Table_Bees.htm.