A mason bee

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A mason bee

Scientific Name

(Osmia chalybea)

Osmia chalybea is one of five wide-ranging mason bees considered to be uncommon to rare in the eastern United States. The lack of information is likely due to limited collection efforts historically. Despite this, the species appears to be stable at least in the short term (1). Osmia chalybea ranges across the east and southeastern coastline, from New York to Texas, extending into some landlocked states (1, 2). In Maryland, the species was found on the coast of Worcester County over a decade ago (3).

Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.

Identification

Osmia chalybea is distinct from other mason bees in having dark brown wings (4). The species has a metallic blue body primarily covered in white hairs (2). In general, female mason bees are slightly larger than males and carry pollen under their abdomen rather than on their legs. Male mason bees are slender in antennae and body (5, 6). Female O. chalybea have the lateral ocelli on the top of the head closer to each other than to the eyes, while males are about equal in distances. In addition, the color of the spurs on the middle and hind legs slightly differs in shade of brown between males and females (2).

Male. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.

Male. Photo by Margarita Miklasevskaja from Bees of Canada.Image courtesy of Mikalsevskaja at PCYU with funding from NSERC-CANPOLIN.

Female. Photo by Margarita Miklasevskaja from Bees of Canada.Image courtesy of Mikalsevskaja at PCYU with funding from NSERC-CANPOLIN.

Life cycle

Osmia chalybea, like most mason bees, is solitary and a cavity nester (5, 6, 7). A female mason bee emerges from the nest it developed in, and a few days after, it searches for a space to nest in (6). Female O. chalybea arrange their nest cells linearly, separating them with chewed-up leaves. While gathering pollen, the female also collects nectar in its stomach to mix with the pollen piled in the cell (6, 7). After mating, the egg is placed in a cell, feeds on the provisions once hatched, and develops into an adult that overwinters (7).

Osmia chalybea typically is in flight from March to May, in spring (2). However, in Maryland, the species appears to emerge later in summer (8). While most mason bees are generalists, O. chalybea has been observed to be specialized, targeting flowers in the Cirsium genus (2, 5, 6, 7, 8).

Habitat

Osmia chalybea, like most mason bees, has been observed to nest in wooden blocks with holes (5, 6, 7). The species can be found in a wide variety of habitats, such as prairies, grasslands, savannas, and shores (1, 3, 7).

Distribution in Maryland

Data from Maryland Biodiversity Project.

Distribution in US

Data from NatureServe Explorer.

How can you help?

As O. chalybea is a specialist, planting the favorite flowers of the species, notably C. horridulum, can help the species (7). Providing cavities for O. chalybea to nest in would also benefit the species, such as leaving wooden blocks or straw bundles in your backyard (6).

Example of Plants

Yellow thistle

(Cirsium horridulum)

Photo by Lauren Smith.Under the license: Creative Commons Attribution-Share Alike 4.0 International.

Bull thistle

(Cirsium vulgare)

Photo by Peripitus.Under the license: Creative Commons Attribution-Share Alike 3.0 Unported.

References

Schweitzer, D. F. and M. Ormes. 2021. Osmia chalybea a mason bee. NatureServe. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.837229/Osmia_chalybea. Last accessed 20 April 2022.
Mitchell, T. B. 1960. Bees of the Eastern United States II. North Carolina Agricultural Experiment Station, 2(152): 84-85.
Droege, S. 2017. Information on record USGS_DRO213231. Discover Life. https://www.discoverlife.org/mp/20l?id=USGS_DRO213231. Last accessed 20 April 2022.
Michener, C. D. 1936. Some North American Osmiinae (Hymenoptera, Apoidea). The American Museum of Natural History, (875):23.
Carril, O. M., and J. S. Wilson. 2021. Common Bees of Eastern North America. Princeton University, 123: 123.
Carril, O. M. and Wilson, J. S. 2015. The Bees in Your Backyard: A Guide to North America's Bees. Princeton University, 153-166.
Rozen Jr., J. G., and Hall, H. G. 2011. Nesting and Developmental Biology of the Cleptoparasitic Bee Stelia ater (Anthidiini) and Its Host, Osmia chalybea (Osmiini) (Hymenoptera: Megachilidae). The American Museum of Natural History, 3707.
Fowler, J. 2016. Specialist Bees of the Mid-Atlantic: Host Plants and Habitat Conservation. The Maryland Entomologist, 6:(4). https://www.mdentsoc.org/wp-content/uploads/2018/11/The-Maryland-Entomologist-2016.pdf. Last accessed 20 April 2022.

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