What structural element differentiates *Hylaeus* from the solitary wasps it can resemble?
The yellow-faced bee has a broader connection between the thorax and abdomen than a wasp's narrow petiole.
When *Hylaeus* is confused with solitary wasps due to its slender build and smooth surface, the key structural difference lies in the connection between the main body sections. Solitary wasps possess a very narrow constriction, known as the petiole, separating the thorax from the abdomen, creating a distinct 'wasp waist.' Although the yellow-faced bee is slender, its connection between the thorax and abdomen is substantially broader than that narrow petiole found in wasps. Furthermore, wasps typically display white or cream markings on the face, or none at all, providing another differentiating factor against the bright yellow configuration found in *Hylaeus*.
