Bees appear in recent classifications to be a specialized lineage of crabronid wasps that switched to the use of pollen and nectar as larval food, rather than insect prey; this makes the Crabronidae a paraphyletic group. Accordingly, bees and sphecoids are now all grouped together in a single superfamily, and the older available name is "Apoidea" rather than "Sphecoidea" (which, like Spheciformes, has been used in the past, but also defined a paraphyletic group and has been abandoned).
As bees (not including their wasp ancestors) are still considered a monophyletic group, they are given a grouping between superfamily and family to unify all bees, Anthophila (Engel, 2005).
This cladogram is based on Debevic et al 2012, which used molecular phylogeny to demonstrate that the bees (Anthophila) arose from deep within the Crabronidae, which is therefore paraphyletic. The Heterogynaidae is also broken up. The small subfamily Mellininae was not included in their analysis.