Hylaeus verticalis

Taxonomy

Hylaeus verticalis, commonly known as the vertical-faced yellow-faced bee, belongs to the genus Hylaeus in the family Colletidae. Hylaeus is the only truly globally distributed Colletid genus, occurring on all continents except Antarctica. 

Bees in the genus Hylaeus are different than many bees we find nesting in wood or stems; they belong to the family Colletidae, also known as “plasterer bees". Colletidae use a special secretion from their mouths, unique in their family, to line their nests. This family is considered a more ancient family of bees. Bees in the genus Hylaeus are sometimes called “yellow-faced bees” or “masked bees” because of the distinctive yellow markings on their faces.

The geographic distribution of H. verticalis spans across the United States and Canada, particularly in regions with prairie, grassland, and forest habitats. H. verticalis was one of the most identified Hylaeus species in the MN Bee Atlas’ bee blocks.

Description

Hylaeus are very small, black, nearly hairless bees, frequently with yellow or white markings on their faces, collars and legs. Males have more yellow on the face, frequently filling the lower face between the eyes and looking more like a “mask.” Females frequently have yellow face markings restricted to two distinct triangles right near the eyes, sometimes described as “devil horns.” Hylaeus do not have pollen collecting hairs. Instead, they carry pollen and nectar home inside their bodies, in their crop. These are the smallest bees we find in stem or wood nests, and they can be easily mistaken for small Passaloecus wasps because they share similar size, body shape and color, and lack of hair. Passaloecus wasps can be distinguished by the wider, more square “block-head” look to their faces. They also often have silvery hairs on their faces, which Hylaeus bees do not have. Remember, Passaloecus wasps are shy and solitary like our bees, and they stock their nests with hundreds of aphids.

Hylaeus verticalis specimens are easier to identify than some other Hylaeus species as they possess more unique identifying characteristics. They range in size from 6-7mm and have darker-colored bodies with more golden-yellow markings than some other species. Females of this species can be identified as having black bodies with black antennae and scapes. The facial markings of females are golden-yellow to orange and are much longer and narrower than in other species – ending just at the level of the antennae. The collar and tegula are also black, but hind legs and tubercles are usually bright yellow. The wings of H. verticalis are usually quite dark and have strong, dark veins. Their faces have foveae that are deep and linear. They are separated from the eye margin by a slightly wider space than in other species.

Male Hylaeus verticalis are the archetype of the Hylaeus species. Their bodies and antennae are fully black, with the scapes of the antenna being only slightly enlarged. Male wings are lighter than female wings, being mostly clear with brownish veins. This species has golden-yellow to orange markings on its face, mouth area, sides of the face, and legs. The facial markings start just above the clypeus and extend upward between the antennae and into slender projections that partly surround its antennal area. This gives the yellow markings a “devil horn” appearance. Its face is narrow, eyes slant downwards, and cheeks are slightly narrower than its eyes from the side. There are two glossy, mirror-like depressions right behind the scape on the top of the head. The top of its abdomen is rough with deep holes close together on its thorax and more spread out on its sides.

Nest Structure

Unlike Megachilid bees, Hylaeus generally do not bring in outside materials to build their nests. Instead, they use a special secretion from their mouths, sometimes called “bee spit”, to line their nests and make their nest plugs. They have specially shaped tongues with broad ends that aid in “painting” the secretions inside the nests. The secretion dries to a thin, clear, water proof coating for the cells. Hylaeus nests have been known to be submerged in water and still emerge, and many species are associated with wetlands. Hylaeus provision their cells with a semi-liquid combination of nectar and pollen, instead of the more doughy “bee bread” of many solitary bee species. The cell lining is extremely delicate; a cellophane nest plug moves and crinkles easily with the lightest touch of a blade of grass. Plug appearance can vary from an opaque white color to an almost colorless, transparent film, like plastic wrap.

Hole Sizes

Hylaeus bees nest in column 3 holes (1/8-3/16") in Bee Atlas blocks.

Voltinism

We are looking into whether these bees have more than one generation per year and are interested to hear from anyone who has them in their blocks.

Activity Period

No information at this time.

References

Discover Life. (n.d.). Hylaeus verticalis: Identification guide. Retrieved from https://www.discoverlife.org/mp/20q?search=Hylaeus+verticalis&guide=Hylaeus_male (Accessed May 10, 2024).