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Blue Mason Bee - Osmia caerulescens
Length 8 to 10 mm. The females have large box-shaped heads and a blue metallic lustre to the abdomen giving rise to its common name, with a black pollen basket on the hind legs. The males are bronze with pale yellow hairs and a shining slope at the front of the abdomen.
Most solitary bees and wasps are difficult to identify, and can rarely be identified from photos taken in the field. All red-rated records should include a photo or set of photos of the specimen, illustrating the key characters taken from a standard key, which should also be referenced (e.g. ‘Falk, 2015’). The full set of key characters are generally not visible in field photos and photos are rarely sharp enough. To aid in the verification of your records, please include face shot, side, top and wings. The notes should state whether male or female, and explain how the specimen met the key characters. Although NS may not be able to identify the species even if these reference photos are provided, the photos will be stored with the record and may allow it be identified in future. Alternatively, NS will accept records identified by a recognised local or national expert, or that have been identified via BWARS’ Facebook https://www.facebook.com/profile.php?id=100065021433202 . If you have obtained this advice, please note the name of the person/organisation identifying the record in the ‘determiner’ field (e.g. ‘Stuart Roberts, BWARS Facebook’) rather than just a comment of ‘BWARS Facebook’.
Forest edges and clearings, flower meadows, orchards, parks and gardens.
April to August/September.
Nests in holes, often existing cavities in dead wood and plant stems, rocks and mud walls. The female deposits her egg, adds food for the larvae, builds a small wall out of chewed leaves and creates the next chamber, where she will deposit the next egg.
Widespread in England and Wales but more common in the South.
Occasional in Leicestershire and Rutland.
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Species profile
- Common names
- Blue Mason Bee
- Species group:
- Bees, Wasps, Ants
- Kingdom:
- Animalia
- Order:
- Hymenoptera
- Family:
- Megachilidae
- Records on NatureSpot:
- 39
- First record:
- 28/05/2010 (Gould, David)
- Last record:
- 30/07/2023 (Pochin, Christine)
Total records by month
% of records within its species group
10km squares with records
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