Osmia (Cephalosmia)

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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 pubescence on their head, thorax, and abdomen (Michener 2007).

Diagnostic characteristics

(modified from Michener 2007, unless otherwise stated)

• Genal area wider than the greatest width of the eye.
• Hind coxa without strong longitudinal carina along inner ventral angle.
• Malar space shorter than the width of the scape.
• Parapsidal line punctiform.
• Propodeal triangle dull, with densely granulose puncturing (Rightmyer et al. 2013)
• Female clypeus has large, dispersed punctures or, as in Osmia (Cephalosmia) montana, lacks punctures entirely.
• Female mandible is four-toothed.
• Female mandible with a tooth or angle on the inner ventral margin.
• Female T6 is small and lacks hairs in comparison to T5.
• Male S2 not enlarged, posterior margin slightly concave, straight, or slightly convex.
• Male S3 not or weakly emarginate medially and fully exposed.
• Male S6 lacks lateral teeth.

May be confused with

Female O. (Cephalosmia) may be confused with female O. (Hemiosmia) because of the angle or tooth on the inner ventral margin, but can be differentiated by the large, dispersed punctures or the complete lack of punctures on the clypeus (Michener 2007).

Host associations

Osmia (Cephalosmia) have been observed visiting Asteraceae, and three species are known specialists (Cane 2016).

Nesting behavior

Osmia (Cephalosmia) typically nest in abandoned beetle burrows in wood (Michener 2007). Cell partitions are constructed out of macerated leaf materials and sometimes mud (Michener 2007). 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 1974).

Diversity

Osmia (Cephalosmia) contains five species (Michener 2007).

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 2007).

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