Hylaeus annulatus

Taxonomy

Hylaeus annulatus, commonly known as the ringed masked bee, belongs to the genus Hylaeus within 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. 

Hylaeus annulatus is mainly found in North America and Europe. Its North American range extends from Alaska to Nova Scotia, encompassing the New England states, Minnesota, and down to North Carolina and Georgia. 

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 annulatus typically measures between 6 to 7mm in size. Similar to other Hylaeus species, they have slender, hairless black bodies with scattered yellow markings. What sets this species apart are its entirely black collar and scape. The wings of H. annulatus are slightly shaded with dark veins and stigma. In females, yellow to creamy ivory markings are found on the sides of their faces, though they don't extend all the way to their eyes. Most often, a small yellow patch can be found on the rim of the clypeus. Tubercles and leg joints are usually also yellow, with small yellow spots near the top and base of their legs while the remainder is black. Their faces are slender, with eyes converging towards the bottom and distinct, deep foveae not found in closely related species.

Distinguishing males of this species from Hylaeus verticalis can sometimes pose a challenge. However, the scapes of H. annulatus males are enlarged to roughly twice the size of the flagellum and marked by a large, yellow spot. Moreover, the yellow facial markings in these males taper broadly just above the antennae, veering slightly away from the eye's edge.

Nest Structure

Unlike Megachilid bees, Hylaeus 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.) Discover Life: An interactive encyclopedia about the natural world. Available at: https://www.discoverlife.org/mp/20q?search=Hylaeus+annulatus&guide=Hylaeus_male.

(Accessed: May 10, 2024).