Osmia (Cephalosmia)

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Osmiini
Genus: Osmia Panzer, 1806
Subgenus: Cephalosmia Sladen, 1916
Common name: none

Overview

Osmia (Cephalosmia) are large dark blue bees ranging in body length from 8–17 mm, with partly or sometimes entirely black pubescencepubescence:
short, fine hair
on their head, thorax, and abdomen (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

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., unless otherwise stated)

• Genal area wider than the greatest width of the eye.
• Hind coxacoxa:
  the basal segment of the leg
  without strong longitudinal carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  along inner ventralventral:
  of, on, or relating to the underside of an animal, or segment of an animal
  angle.
• Malar space shorter than the width of the scapescape:
  the basal, and usually the longest, segment of the antennae
  .
• 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.
• Propodeal triangle dull, with densely granulose puncturing (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.)
• Female clypeusclypeus:
  a section of the face below the antennae, demarcated by the epistomal sutures
  has large, dispersed punctures or, as in Osmia (Cephalosmia) montana, lacks punctures entirely.
• Female mandiblemandible:
  bee teeth, so to speak, usually crossed and folded in front of the mouth
  is four-toothed.
• Female mandiblemandible:
  bee teeth, so to speak, usually crossed and folded in front of the mouth
  with a tooth or angle on the inner ventralventral:
  of, on, or relating to the underside of an animal, or segment of an animal
  margin.
• Female 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
  is small and lacks hairs in comparison to T5T5:
  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
  .
• 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
  not enlarged, posterior margin slightly concave, straight, or slightly convexconvex:
  curved outward
  .
• Male 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
  not or weakly emarginateemarginate:
  a notched or cut out place in an edge or margin, can be dramatic or simply a subtle inward departure from the general curve or line of the margin or structure being described
  medially and fully exposed.
• Male S6S6:
  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
  lacks laterallateral:
  relating, pertaining, or attached to the side
  teeth.

May be confused with

Female O. (Cephalosmia) may be confused with female O. (Hemiosmia) because of the angle or tooth on the inner ventralventral:
of, on, or relating to the underside of an animal, or segment of an animal
margin, but can be differentiated by the large, dispersed punctures or the complete lack of punctures on the clypeusclypeus:
a section of the face below the antennae, demarcated by the epistomal sutures
(Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Host associations

Osmia (Cephalosmia) have been observed visiting Asteraceae, and three species are known specialists (Cane 2016Cane 2016:
Cane, J.H. 2016. Specialist bees collect Asteraceae pollen by distinctive abdominal drumming ( Osmia ) or tapping ( Melissodes , Svastra ). Arthropod-Plant Interactions 11: 257ndash;261.).

Nesting behavior

Osmia (Cephalosmia) typically nest in abandoned beetle burrows in wood (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Cell partitions are constructed out of macerated leaf materials and sometimes mud (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). The egg is placed inside a small pocket within the center of the pollen store; this is an unusual characteristic, as most eggs are placed in a cell on top of a food mass (Rust 1974Rust 1974:
Rust, R.W. 1974. The systematics and biology of the genus Osmia, subgenera Osmia, Chalcosmia, and Cephalosmia. Wasmann Journal of Biology 32: 1ndash;93.).

Diversity

Osmia (Cephalosmia) contains five species (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Distribution

Osmia (Cephalosmia) can be found in western North America, ranging from the Northwest Territories of Canada to Baja California, Mexico. They are rarely found east of the Great Lakes (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

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

References

Cane, J.H. 2016. Specialist bees collect Asteraceae pollen by distinctive abdominal drumming (Osmia) or tapping (Melissodes, Svastra). Arthropod-Plant Interactions 11: 257-261.

Michener, C.D. 2007. The Bees of the World. 2nd ed. Johns Hopkins University Press, Baltimore and London, 953 pp. Psyche 77: 190-201.

Rightmyer, M.G., T.L. 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.

Rust, R.W. 1974. The systematics and biology of the genus Osmia, subgenera Osmia, Chalcosmia, and Cephalosmia. Wasmann Journal of Biology 32: 1-93.