Ashmeadiella gillettei, copyright C. Ritner.

Belongs within: Megachilidae.
Contains: Megachilini, Osmiina.

The Osmiini are a group of megachilid bees with an arolium and an elongate pterostigma (Engel 2001). Phylogenetic analysis indicates that this group is paraphyletic to the Megachilini (Cardinal et al. 2010). Claws are typically simple though they are cleft in the fossil Baltic amber genus Glyptapis (Engel 2001).

The osmiin mason bees
Published 9 February 2020

As I’m sure I must have had cause to say before, the world of solitary bees is a spectacularly diverse. Literally tens of thousands of species have been described to date, and no doubt many more remain. The classification of bees was reviewed by in great detail by Charles Michener (2007) in his monumental Bees of the World, and it was there that I turned to learn about the subject of today’s post, the osmiins.

Female Osmia ferruginea, copyright Gideon Pisanty.

The Osmiini are currently recognised as a tribe of the Megachilidae, one of the two families of long-tongued bees (the other is the Apidae, including, among others, the majority of social bees). Megachilids are most easily characterised by the position of the scopa, a dense array of hairs used by bees for carrying pollen. In most bees possessing a scopa (it tends to be reduced or lost in kleptoparasitic forms), it is located on the hind legs but in megachilids it covers the underside of the metasoma. Osmiins are distinguished from other megachilids by the combination of a well developed sting, elongate stigma on the fore wing, arolia between the claws, and the lack of a pygidial plate. They are often smaller bees, less than a centimetre in length, though the largest osmiins grow close to two centimetres. Some osmiins are also more or less metallic in coloration, an unusual condition for megachilids. No feature has been identified that is unique to osmiins as a whole and their monophyly relative to other megachilid tribes (particularly the Megachilini) has long been called into question. A number of authors have recognised a division of living osmiins between two subtribes, the Osmiina and Heriadina. Osmiina have generally been distinguished from Heriadina by features such as a smaller stigma in the fore wing, a mesopleuron (a plate forming much of the side of the mesosoma) that is shorter ventrally than dorsally, and a propodeum that generally slopes downward from the base (rather than being initially flat). Again, however, the validity of this division has been questioned as no one feature uniformly distinguishes the two groups. A phylogenetic analysis of the Megachilidae by Gonzalez et al. (2012) did not support monophyly for Osmiini or either of its subtribes, but a proper revision of the group’s higher classification remains to be done.

Female Hoplitis parana, copyright Gideon Pisanty.

Like other solitary bees, osmiins nest in cavities (a handful are kleptoparasites that do not construct their own nests). They often do not construct these cavities themselves but occupy pre-existing ones such as abandoned beetle burrows and hollows in wood, or crevices between rocks. Some species of Osmia have a predilection for nesting in empty snail shells. Cells are most commonly demarcated in the nest by walls constructed of chewed leaves, often held together with a sticky substance such as mud, resin or (more rarely) nectar. In some cases, the amount of leaf material used is reduced or abandoned, so the cell walls are made entirely of mud or resin. In some European species of Hoplitis, the cells are lined with petals; the species H. papaveris, for instance, lines its cells with bright red poppy petals. Osmia brevicornis, a species found in southern Europe and central Asia, is unusual in that its nest is not divided into cells. Instead, the nest cavity (an abandoned beetle burrow) is uniformly packed with pollen, with eggs being progressively inserted into the pollen mass as it is laid down. The larvae feed on the pollen around them after they hatch, and cocoons end up randomly scattered through the remains of the mass as they mature.

Systematics of Osmiini

Characters (from Engel 2001): Arolium present; claws simple (rarely cleft). Pterostigma longer than wide; 2m-cu basad 2rs-m. Integument usually without maculations, frequently metallic or with metallic highlights.

<==Osmiini [Chelostomidae, Glyptapidae, Osmiinae, Osmiites, Trypetini]CSD10
    |--+--Afroheriades hyalinusCSD10
    |  `--MegachiliniCSD10
    `--+--Chelostoma Latreille 1809CSD10, E01
       |    |--C. californicum Cresson 1878CSD10
       |    |--C. (Foveosmia) campanularumH-DY-O05
       |    |--C. culmorumL49
       |    |--C. florisomneK62
       |    |--C. mauritanica Lucas 1848E12
       |    |--C. maxillosaG20 [=Hylaeus maxillosusL02, Megachile (Chelostoma) maxillosaG20]
       |    `--C. (Gyrodromella) rapunculi [incl. Apis fuliginosa (preoc.), C. fuliginosum, C. nigricorne]H-DY-O05
       `--+--+--Protosmia rubifloris (Cockerell 1898)CSD10
          |  `--Heriades Spinola 1808CSD10, E01 [incl. Trypetes Schenck 1861E01; Heriadini, Trypetina]
          |       |--H. campanularum [=Megachile (Heriades) campanularum]G20
          |       |--H. crucifer Cockerell 1897CSD10
          |       |--H. leavittiBD17
          |       |--H. parvulaR35
          |       `--H. truncorumPK17
             |    |--H. albifrons (Kirby 1837)CSD10
             |    |--H. (Hoplitis) anthocopoidesH-DY-O05
             |    |--H. bullifaciesG05
             |    |--H. palmarumG05
             |    `--H. productusO02
             `--+--+--Hoplosmia scutellaris (Morawitz 1868)CSD10
                |  `--OsmiinaCSD10
                     |--A. aridula Cockerell 1910CSD10
                     |--A. bigeloviaeG05
                     |--A. bucconisC01
                     |--A. cactorumC01
                     |--A. cubicepsG05
                     |--A. gilletteiG05
                     `--A. rufipesG05
Osmiini incertae sedis:
  Apiaria Germar 1839E01
    `--*A. dubia Germar 1839E01
  Glyptapis Cockerell 1909 [Glyptapina, Glyptapinae]E01
    |--*G. mirabilis Cockerell 1909E01
    |--G. densopunctata Engel 2001E01
    |--G. disareolata Engel 2001E01
    `--G. fuscula Cockerell 1909 (see below for synonymy)E01
  Andronicus cylindricus [incl. Hoplitis monardae]R35
    |--A. hypocritaR35
    `--A. productaR35

Glyptapis fuscula Cockerell 1909 [incl. G. neglecta Salt 1931, G. reducta Cockerell 1909, G. reticulata Cockerell 1909]E01

*Type species of generic name indicated


[BD17] Branstetter, M. G., B. N. Danforth, J. P. Pitts, B. C. Faircloth, P. S. Ward, M. L. Buffington, M. W. Gates, R. R. Kula & S. G. Brady. 2017. Phylogenomic insights into the evolution of stinging wasps and the origins of ants and bees. Current Biology 27: 1019–1025.

[CSD10] Cardinal, S., J. Straka & B. N. Danforth. 2010. Comprehensive phylogeny of apid bees reveals the evolutionary origins and antiquity of cleptoparasitism. Proceedings of the National Academy of Sciences of the USA 107 (37): 16207–16211.

[C01] Cockerell, T. D. A. 1901. Contributions from the New Mexico Biological Station.—X. Observations on bees collected at Las Vegas, New Mexico, and in the adjacent mountains. Annals and Magazine of Natural History, series 7, 7: 125–131.

[E01] Engel, M. S. 2001. A monograph of the Baltic amber bees and evolution of the Apoidea (Hymenoptera). Bulletin of the American Museum of Natural History 259: 1–192.

[E12] Evenhuis, N. L. 2012. Publication and dating of the Exploration Scientifique de l’Algérie: Histoire Naturelle des Animaux Articulés (1846–1849) by Pierre Hippolyte Lucas. Zootaxa 3448: 1–61.

[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.

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: 261–286.

[G05] Grissell, E. E. 2005. A review of North American species of Microdontomerus Crawford (Torymidae: Hymenoptera). Journal of Hymenoptera Research 14 (1): 22–65.

[H-DY-O05] Hinojosa-Díaz, I. A., O. Yáñez-Ordóñez, G. Chen, A. T. Peterson & M. S. Engel. 2005. The North American invasion of the giant resin bee (Hymenoptera: Megachilidae). Journal of Hymenoptera Research 14 (1): 69–77.

[K62] Krombein, K. V. 1962. Natural history of Plummers Island, Maryland. XVI. Biological notes on Chaetodactylus krombeini Baker, a parasitic mite of the megachilid bee, Osmia (Osmia) lignaria Say (Acarina: Chaetodactylidae). Proceedings of the Biological Society of Washington 75: 237–250.

[L02] Latreille, P. A. 1802. Histoire Naturelle des Fourmis, et recueil de mémoires et d’observations sur les abeilles, les araignées, les faucheurs, et autres insectes. Théophile Barrois père: Paris.

[L49] Lucas, H. 1849. Exploration Scientifique de l’Algérie pendant les années 1840, 1841, 1842 publiée par ordre du gouvernement et avec le concours d’une commission académique. Sciences physiques. Zoologie. II. Histoire naturelle des animaux articulés. Troisième partie. Insectes (suite). Imprimerie Nationale: Paris.

Michener, C. D. 2007. The Bees of the World 2nd ed. John Hopkins University Press: Baltimore.

[O02] Opitz, W. 2002. Cleridae Latreille 1804. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 267–280. CRC Press.

[PK17] Peters, R. S., L. Krogmann, C. Mayer, A. Donath, S. Gunkel, K. Meusemann, A. Kozlov, L. Podsiadlowski, M. Petersen, R. Lanfear, P. A. Diez, J. Heraty, K. M. Kjer, S. Klopfstein, R. Meier, C. Polidori, T. Schmitt, S. Liu, X. Zhou, T. Wappler, J. Rust, B. Misof & O. Niehuis. 2017. Evolutionary history of the Hymenoptera. Current Biology 27 (7): 1013–1018.

[R35] Rayment, T. 1935. A Cluster of Bees: Sixty essays on the life-histories of Australian bees, with specific descriptions of over 100 new species. Endeavour Press: Sydney.


    1. I don't know; my general aim on this site is to represent what has been proposed in the literature rather than expressing my own preferred system. I should note that I probably don't have every genus of osmiin listed, though.

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