Check out Clare Maffei and Sam Droege's Videos on how to identify bees using a microscope.
Download Sam Droege's Handy Bee Manual v.2.0 (pdf)
Download Sam Droege's Handy Bee Manual v.2.0 (docx)

Mike Arduser's "Key to the genera and species of the Midwestern United States with an emphasis on the Tallgrass Prairie region. The zipped file contains individual word documents that contain the keys.

The Bees of Maryland
Version 1.0 of The Bees of Maryland

Insect label making tools.