Hylaeus mana is similar in structure to other hymenopterans (bees, wasps, and ants) in that adults have three main body parts-a head, thorax, and abdomen. One pair of antennae arises from the front of the head, between the eyes. Two pairs of wings and three pairs of legs are attached to the thorax. The abdomen is composed of multiple segments (Borror et al. 1989, pp. 665-666). The Hylaeus genus, which includes Hylaeus mana, are commonly known as yellow-faced bees or masked bees for their yellow-to-white facial markings. All of the Hylaeus species roughly resemble small wasps in appearance, due to their slender bodies and their seeming lack of setae (sensory hairs). However, Hylaeus bees have plumose (branched) hairs on the body that are longest on the sides of the thorax. To a discerning eye, it is these plumose setae that readily distinguish them from wasps (Michener 2000, p. 55). This species is an extremely small, gracile (gracefully slender) black bee with yellow markings on the face. The smallest of all Hawaiian Hylaeus species, H. mana is a member of the Dumetorum species group. The face of the male is largely yellow below the antennae, extending dorsally in a narrowing stripe. The female's face has three yellow lines, one against each eye, and a transverse stripe at the apex of the clypeus (lower face region). The female’s other markings are the same as the male’s (Daly and Magnacca 2003, p. 135). Hylaeus mana can be distinguished from H. mimicus and H. specularis, species with overlapping ranges, by its extremely small size, the shape of the male’s genitalia, the female’s extensive facial marks, and a transverse rather than longitudinal clypeal marking (Daly and Magnacca 2003, p. 138).