Photo: Arnstein Staverløkk / NINA / CC BY 3.0
Osmia caerulescens
Blue Mason Bee
A small mason bee (8–10 mm) with a metallic blue-black body, oversized box-shaped head, and black ventral scopa in females. Males are metallic green with ginger hairs. It nests in pre-existing cavities in dead wood, walls, and bee hotels, building cell partitions from leaf mastic. It is bivoltine, flying from April to July and again in August. In Switzerland it is common and widespread in gardens, parks, and woodland edges throughout the lowlands. Swiss Red List: Least Concern (LC).
Species Facts
- Size
- 8–10 mm
- Flight Period
- April to August (bivoltine)
- Nesting
- Cavities
- Specialization
- Generalist
- Abundance
- Common
- Family
- Megachilidae
External Sources
This data has been cross-referenced with national sources:
Data Source & Copyright
| Category | Source / Author | License |
|---|---|---|
| Photo | Arnstein Staverløkk / NINA | CC BY 3.0 |
| Taxonomy & Distribution | InfoFauna Switzerland | Public data |
| Global Distribution | GBIF | CC BY 4.0 |
Data Quality
High Quality Last audit: 2026-05-22
Completeness: 100%
✓Photo exists✓Traits consistent✓Description quality✓Red List referenced✓Attribution verified
Confidence: 67%
IdentifiabilityMediumImage confidenceMediumImage qualityHighTrait coherenceHigh
