Osmia

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Osmiini
Genus: Osmia Panzer, 1806
Subgenera: Allosmia, Cephalosmia, Diceratosmia, Erythrosmia, Euthosmia, Helicosmia, Hemiosmia, Hoplosmia, Melanosmia, Metallinella, Mystacosmia, Nasutosmia, Neosmia, Osmia, Pyrosmia, Tergosmia, Trichinosmia
Common name: mason bees

Overview

Bees in the genus Osmia are commonly referred to as “mason bees,” due to their habit of using mud, pebbles, or chewed leaf material to build nest compartments. Osmia means “odor,” which refers to the lemony scent the bees produce when marking their nest entrances (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). This secreted odor allows them to distinguish their nest entrance from other Osmia nesting entrances found nearby (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). They generally have a short, robust body form and range in body length from 7–13 mm (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Coloration ranges from metallic green to blue to black (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Diversity

Osmia contains more than 350 species in 20 subgenera worldwide (Müller 2018b; Rightmyer et al. 2013Rightmyer et al. 2013:
Rightmyer, M.G., T. Griswold, and S.G. Brady. 2013. Phylogeny and systematics of the bee genus Osmia (Hymenoptera: Megachilidae) with emphasis on North American Melanosmia : subgenera, synonymies, and nesting biology revisited. Systematic Entomology 38: 561-576.).

Diagnostic characteristics

(modified from Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.)

• Arolia present.
• Stigma stigma:
  a pigmented/ thickened spot on the costal margin of the forewing, usually at the end of the radius(Greek, stigma= mark)
  more than twice as long as broad.
• Mesopleuron not elongate, distinctly shorter than the length of the scutumscutum:
  the large segment on top of the thorax located between the wings and behind the head
  .
• Metanotum metanotum:
  the posterior dorsal segment of the thorax, behind the scutellum
  sloping abruptly so that it faces posteriorly.
• T1 without raised carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  between the anterioranterior:
  toward the head or on the head side of a segment being described
  and dorsaldorsal:
  in general, the upper surface
  surfaces.
• Parapsidal line parapsidal line:
  the line that runs submedially along the scutum and corresponds to the median border of the site of origin for flight muscles
  punctiform (except in subgenera Allosmia, Erythrosmia, and Tergosmia, all Osmiini) with punctiform parapsidal lines.
• Pronotal lobes without carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  .
• Male S2S2:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  enlarged and covering much of S3S3:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  .
• Male T6T6:
  the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
  laterallateral:
  relating, pertaining, or attached to the side
  tooth absent.

May be confused with

Osmia may be confused with Stelis and Hoplitis due to similar shape and coloration, but can usually be differentiated by the elongate parapsidal lineparapsidal line:
the line that runs submedially along the scutum and corresponds to the median border of the site of origin for flight muscles
in Hoplitis and the lack of scopal hairs in the females of Stelis (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Known invasives

Osmia caerulescens is native to Europe and North Africa and was accidentally introduced to the U.S. sometime in the 1800s. It has been collected in the northeastern and north-central half of the U.S., but it is not as common as it once was (Sheffield et al. 2011).

Osmia cornifrons is native to Japan but was intentionally introduced to the U.S. in the 1960s to pollinate orchards and is still used commercially (Bosch et al. 2008Bosch et al. 2008:
Bosch, J., F. Sgolastra, and W.P. Kemp. 2008. Life cycle ecophysiology of Osmia mason bees used as crop pollinators. Bee Pollination in Agricultural Ecosystems. Oxford University Press, New York, pp. 83ndash;104.). It has since been used to pollinate blueberries, melons, strawberries, legumes, and mustard crops. There are now naturalized populations in the Mid-Atlantic and northeastern U.S. (Bosch et al. 2008Bosch et al. 2008:
Bosch, J., F. Sgolastra, and W.P. Kemp. 2008. Life cycle ecophysiology of Osmia mason bees used as crop pollinators. Bee Pollination in Agricultural Ecosystems. Oxford University Press, New York, pp. 83ndash;104.). A few specimens have been collected in Oregon, but populations do not appear to have become established.

Osmia cornuta is native to Europe and North Africa and was intentionally introduced to the U.S. in the 1980s to pollinate crops (Torchio and Asensio 1985Torchio and Asensio 1985:
Torchio, P. and E. Asensio. 1985. The introduction of the European bee, Osmia cornuta Latr, into the US as a potential pollinator of orchard crops, and a comparison of its manageability with Osmia . Journal of the Kansas Entomological Society 58: 42ndash;52.). Established wild populations of this species have not been documented.

Osmia taurus is native to Asia and was accidentally introduced to the U.S. as early as 2000 and is now common along the eastern part of the country (Russo 2016Russo 2016:
Russo, L. 2016. Positive and negative impacts of non-native bee species around the world. Insects 7: 69.). It looks very similar to O. cornifrons, and they are easily mistaken. This could be why O. taurus was introduced to the U.S. (Giles and Ascher 2006Giles and Ascher 2006:
Giles, V. and J.S. Ascher. 2006. A survey of the bees of the Black Rock Forest Preserve, New York (Hymenoptera: Apoidea). Journal of Hymenoptera Research 15: 208ndash;231.).

Host associations

Many Osmia are generalists and will collect pollen from a range of flowering plants. Flowers that are favored by Osmia are often tube-shaped or asymmetrical, such as plants in the family Fabaceae (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.).

Nesting behavior

Osmia nest in pre-existing cavities, such as snail shells, abandoned nests, rock fissures, dead wood, and hollow stems, using mud, pebbles, or chewed leaf material to build nest compartments (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.; Gonzalez et al. 2012Gonzalez et al. 2012:
Gonzalez, V.H., T. Griswold, C.J. Praz, B.N. Danforth. 2012. Phylogeny of the bee family Megachilidae (Hymenoptera: Apoidea) based on adult morphology. Systematic Entomology 37: 261ndash;286.). They do not form colonies or hives, but may nest in close proximity to one another.

Distribution

Osmia are widely abundant throughout Europe, the Mediterranean Basin, southwestern Asia, and western North America (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Over 130 species are found in the United States and Canada (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Fewer than 30 species occur east of the Mississippi River (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Osmia thrive at a wide range of elevations, from sea level to high above the tree line, and are common in regions with temperatures that drop below 0° C.

​Distribution map generated by Discover Life -- click on map for details, credits, and terms of use.

References

Bosch, J., F. Sgolastra, and W.P. Kemp. 2008. Life cycle ecophysiology of Osmia mason bees used as crop pollinators. Bee Pollination in Agricultural Ecosystems. Oxford University Press, New York, pp. 83-104. 

Giles, V. and J.S. Ascher. 2006. A survey of the bees of the Black Rock Forest Preserve, New York (Hymenoptera: Apoidea). Journal of Hymenoptera Research 15: 208-231.

Gonzalez, V.H., T. Griswold, C.J. Praz, and B.D. Danforth. 2012. Phylogeny of the bee family Megachilidae (Hymenoptera: Apoidea) based on adult morphology. Systematic Entomology 337:261-286.

Michener, C.D. 2007. The Bees of the World. 2nd ed. Johns Hopkins University Press, Baltimore and London, 953 pp.

Müller, A. 2018. Palaearctic Osmiine Bees, ETH Zürich, http://blogs.ethz.ch/osmiini

Russo, L. 2016. Positive and negative impacts of non-native bee species around the world. Insects 7: 69.

Sheffield, C., S. Dumesh, and M. Cheryomina. 2011. Hylaeus puntatus (Hymenoptera: Colletidae), a bee species new to Canada, with notes on other non-native species. Journal of the Entomological Society of Ontario 142: 29-43.

Torchio, P. and E. Asensio. 1985. The introduction of the European bee, Osmia cornuta Latr into the US as a potential pollinator of orchard crops, and a comparison of its manageability with Osmia. Journal of the Kansas Entomological Society 58:42-52.

Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North America’s Bees. Princeton University Press.