Males of Lasioglossum calceatum and Lasioglossum albipes are almost impossible to separate to species from photographs without a view of the colour of the labrum. The labrum is a small oval plate located below the clypeus on the front of the head, and it is often "folded up" underneath the head in front of the mandibles making it difficult to see. Both species have yellow and black markings on the clypeus, so it is important to be sure that you are looking at the labrum itself, not the clypeus. The following photos show the faces of males of both species with the labrum "unfolded" and visible.The Lasioglosum albipes male, on the left, has a yellow labrum below the clypeus. The Lasioglossum calceatum male, on the right, has a black labrum below the clypeus.
If the labrum is folded away, then a photo of the head from underneath is required to make an ID. This is a Lasioglossum calceatum male with the oval black labrum "folded away" under the head in front of the mandibles. The yellow colouring visible in front of the labrum is the lower part of the clypeus. Photos credit Andy Kaey