Hylaeus is a large (over 500 species) and diverse cosmopolitan genus within the bee family Colletidae. This genus is also known as the yellow-faced bees or masked bees. This genus is the only truly globally distributed colletid, occurring on all continents except Antarctica. Description The genus of bees consists of generally small, black and yellow/white wasp-like species. The resemblance to wasps is enhanced by the absence of a scopa, which is atypical among bees. The body form of this genus is described as hylaeiform - slender, the hairs inconspicuous without magnification; scopa inconspicuous or absent. Males have an intermediate glossal shape with a small to distinct median apical glossal point. Hylaeus carry pollen in the crop, rather than externally, and regurgitate it into the cell where it will be used as larval food. Like most colletids, the liquid provisions are sealed inside a membranous cellophane-like cell lining. Nests are typically in dead twigs or plant stems, or other similarly small natural cavities, rather than constructing or excavating their own nests as in many other bees. Some species of Hylaeus have been associated with strong scents. In particular, European species such as Hylaeus prosopis are characterised by having a strong "lemon-like" scent. Further investigation has attributed this scent to a substance generated by the manibular glands of both males and females, composed of neral and geranial. It is believed this substance is used as a defensive secretion and/or a social pheromone. Hylaeus Subgenera At least 44 subgenera of Hylaeus are known in the world. These have been categorized geographically as follows by Ikudome (1989): Australasian Region (19 subgenera): Analastoroides, Edriohylaeus, Euprosopellus, Euprosopis, Euprosopoides, Gnathoprosopis, Gnathoprosopoides, Hylaeorhiza, Hylaeteron, Laccohylaeus, Macrohylaeus, Meghylaeus, Planihylaeus, Prosopisteroides, Prosopisteron, Pseudhylaeus, Rhodohylaeus, Spearhylaeus and Xenohylaeus. Palearctic Region (12 subgenera): Abrupta, Dentigera, Hylaeus, Koptogaster, Lambdopsis, Mehelyana, Nesohylaeus, Nesoprosopis, Paraprosopis, Patagiata, Prosopis and Spatulariella. Nearctic Region (7 subgenera): Cephalylaeus, Hylaeana, Hylaeus, Metziella, Paraprosopis, Prosopella and Prosopis. Holarctic Region (3 subgenera): Hylaeus, Paraprosopis and Prosopis. Oriental Region (5 subgenera): Gnathlaeus, Hoploprosopis, Nesoprosopis, Nesylaeus and Paraprosopis. Ethiopian Region (4 subgenera): Alfkenylaeus, Cornylaeus, Deranchylaeus and Metylaeus. Neotropical Region (4 subgenera): Gongyloprosopis, Hylaeana, Hylaeopsis and Prosopis. Distribution and status A significant diversity of Hylaeus is found in Hawai'i — approximately sixty species are recorded as living there. Hylaeus are the only bees considered native to the islands and most of those are unique to the island chain; the diversity of this genus is far