Osmia lignaria

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Osmiini
Genus: Osmia Panzer, 1806
Subgenus: O. (Osmia) Panzer, 1806
Species: Osmia lignaria Say, 1837
Common name: blue orchard bee

Overview

Osmia (Osmia) lignaria are dark metallic blue bees. They have a pale blue face that is covered with a mixture of white and black hair. The thorax has intermixed pale and black hair on the scutum and primarily black hair on the episternum. T1 and sometimes T2 are covered in white hair, and the remaining terga are covered with primarily black hair (Fig 6). Female body length is 7–13 mm, and male body length is 9–11 mm (Sandhouse 1939; Rust 1974).

Diagnostic characteristics 

(from Sandhouse 1939; Rust 1974)

  • Mouthparts usually much smaller than the length of the entire body when extended.
  • Terga without apical hair bands.
  • Female clypeus with short lateral horns in O. lignaria lignaria but lacking or with small protuberances in O. lignaria propinqua.
  • Female mandible is tridentate or four-toothed depending on the subspecies; O. lignaria lignaria is tridentate, whereas O. lignaria propinqua is four-toothed.
  • Female malar space has a projection or lobate process.
  • Female scopa black.
  • Male gonocoxites with subapical ventral projection.
  • Male hind basitarsus with a ventral tooth.
  • Male middle femur with subtriangular ventral projection.

May be confused with 

Osmia lignaria be distinguished from other Osmia (Osmia) by its distinct blue-green hue in combination with the distinctly projected malar space in females and the subtriangular projection on the middle femur in males (Rust 1974). There are, however, two subspecies in the U.S., O. lignaria lignaria and O. lignaria propinqua, which can be more difficult to tell apart. Female O. lignaria lignaria can be distinguished from O. lignaria propinqua by their tridentate mandibles and the short lateral horns on their clypeus (Rust 1974). Males do not have reliable characters to distinguish between the subspecies (Rust 1974).

Phenology

Osmia lignaria adults have been recorded in flight in every month except for November (GBIF 2019d). In the U.S. O. lignaria have been collected in the spring, from March to June (Rust 1974).

Host associations 

Osmia lignaria are polylectic (Torchio 1976). Osmia lignaria are used to pollinate apple, plum, cherry, and almond trees (Torchio 1976; Bosch et al. 2000; Bosch et al. 2006). They have also been observed visiting currant, dandelion, white clover, hawthorn, and rose (Torchio 1976; Phillips and Klostermeyer 1978).

Nesting behavior 

Osmia lignaria often nests in abandoned burrows and hollow stems (Guisse and Miller 2011) . O. lignaria will also nest in man-made nesting materials, such as hollow nesting tubes or drilled wood blocks, allowing them to be collected and transferred to commercial orchard environments (Torchio 1976; Torchio and Asensio 1985). Each nest cavity contains multiple cells separated by mud partitions (Guisse and Miller 2011).

Distribution

Osmia lignaria is native to North America and split into two subspecies: O. lignaria propinqua which is found west of the 100th meridian, and O. lignaria lignaria which is found east of the 100th meridian (Guisse and Miller 2011). All populations occur between sea level and 2000 m (Guisse and Miller 2011). O. lignaria are known to occur from the northern edge of Mexico to the southern half of Canada (Rust 1974). O. lignaria have also been documented in orchard fields in Spain, but it is unknown if they have become established (Ortiz-Sanchez 2011).


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

<p><em>Osmia lignaria</em> female face, photo: Chelsey Ritner</p>
Osmia lignaria female face, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> female lateral habitus, photo: Chelsey Ritner</p>
Osmia lignaria female lateral habitus, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> female abdomen, photo: Chelsey Ritner</p>
Osmia lignaria female abdomen, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> male face, photo: Chelsey Ritner</p>
Osmia lignaria male face, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> male lateral habitus, photo: Chelsey Ritner</p>
Osmia lignaria male lateral habitus, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> male abdomen, photo: Chelsey Ritner</p>
Osmia lignaria male abdomen, photo: Chelsey Ritner
<p><em>Osmia lignaria</em> male, dorsal view of seventh tergum (T7), photo: Chelsey Ritner</p>
Osmia lignaria male, dorsal view of seventh tergum (T7), photo: Chelsey Ritner
<p><em>Osmia lignaria </em>male, diagram showing the genitalia with the dorsal view on the left side and the ventral view on the right, diagram modified from Rust 1974</p>
Osmia lignaria male, diagram showing the genitalia with the dorsal view on the left side and the ventral view on the right, diagram modified from Rust 1974