Hylaeus anthracinus was historically known from numerous coastal and lowland dry forest habitats up to 2,000 ft (610 m) in elevation on the islands of Hawaii, Maui, Lanai, Molokai, and Oahu, and in some areas was ‘‘locally abundant. All Hylaeus bees roughly resemble small wasps in appearance; however, Hylaeus bees have plumose (branched) hairs on the body that are longest on the sides of the thorax, which readily distinguish them from wasps (Michener 2000, in litt.). The anthracinan yellow-faced bee is a medium sized, black bee in the family Colletidae and subfamily Hylaeinae. The species has clear to smoky colored wings and black legs. The male has an oval yellow mark on its face that covers the entire clypeus (lower face region), and a narrow yellow strip below the antennal sockets that runs alongside the clypeus (front of the face). The female is entirely black. The anthracinan yellowfaced bee female has black hairs on the end of the abdomen and an unusual mandible with three teeth, which is a character only shared with its sister species on Kauaʻi, Hylaeus flavifrons (Daly and Magnacca 2003, p. 53). A more detailed description of the species can be found in Daly and Magnacca (2003, pp. 81–83).