An oil-collecting bee

Scientific Name

(Macropis ciliata)

Macropis ciliata is a rare species that, until recently, had not been reported for about a century (1). Macropis bees in general are specialists of one flower genus (Lysimachia), meaning their existence depends on those plants. It is likely that M. ciliata has declined due to Lysimachia flowers declining first (2). The species historically ranged from Maine to Virginia and west towards the Great Plains, also extending into Canada (3). In Maryland, M. ciliata was rediscovered in Washington County, and then in Prince George's County a few years later (1, 4).

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

Identification

Macropis bees in general have a black body covered in white hairs, a head wider than long, and an abdomen with thin white bands. In general, males have a yellow mouth plate. There are four species of Macropis bees in the eastern United States (3). When comparing females, M. ciliata can be distinguished from the others if there are pale hairs on the hind basitarsus and if the thoracic segment joined to the first abdominal one is smooth and polished. When comparing males, M. ciliata has small pits on a shiny abdomen and reduced spurs on its hind tibiae (3).

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

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

Life cycle

Macropis bees are solitary ground nesters whose nests are reused by successive generations. In contrast to other ground-nesting species, they build shallow, compact nests (5). Macropis bees are in flight from May to August, and peak nesting activity is said to be from June to July (2, 3). As is the case with many solitary bees, Macropis males emerge first to ensure there are mates for when the females emerge after. Upon emerging, female bees visit Lysimachia flowers to feed on pollen, then built their nests (6). They return to the flowers to collect floral oil to line their nests and also mix it with pollen to feed their offspring. As Lysimachia does not produce nectar, Macropis bees have to visit other plants for it (5, 6).

Macropis bees are parasitized by Epeoloides pilosula, the Macropis cuckoo bee (2).

Habitat

Macropis bees prefer to nest in well-drained soil on sloped sandy banks with some plants to camouflage their nests (2, 5, 6). They nest near wet habitats where Lysimachia grows, such as swamps, and body of water margins (2).

Distribution in Maryland

Data from Maryland Biodiversity Project.

Distribution in US

Data from NatureServe Explorer.

How can you help?

Planting and preserving Lysimachia flowers, especially in easily accessible areas, will not only help M. ciliata, but also its cleptoparasite, E. pilosulus (2).

Example of Plants

Whorled loosestrife

(Lysimachia quadrifolia)

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

Fringed loosestrife

(Lysimachia ciliata)

Photo by Agnieszka Kwiecień.Under the license: Creative Commons Attribution-Share Alike 4.0 International.

References

Eastern Ecological Science Center. 2019. Macropis ciliata, F, Side, MD, Washington County. USGS. https://www.usgs.gov/media/images/macropis-ciliata-f-side-md-washington-county. Last accessed 20 April 2022.
Ascher, J. S., and C. S. Sheffield. 2005. Red List of Pollinator Insects. Species profile: Epeoloides pilosula, a cleptoparasite of Macropis oil bees. The Xerces Society of Invertebrate Conservation. https://xerces.org/sites/default/files/2019-10/epeoloides_pilosula.pdf. Last accessed 20 April 2022.
Carril, O. M., and J. S. Wilson. 2021. Common Bees of Eastern North America. Princeton University, 123: 103-107.
Droege, S. 2019. Information on record USGS_DRO574418. Discover Life. https://www.discoverlife.org/mp/20l?id=USGS_DRO574418. Last accessed 20 April 2022.
Carril, O. M. and Wilson, J. S. 2015. The Bees in Your Backyard: A Guide to North America's Bees. Princeton University, 111-117.
Schäffler, I. and Dötterl, S. 2011. A day in the life of an oil bee: phenology, nesting, and foraging behavior. Apidologie, (42): 409-424.

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