Two-coloured Mason Bee
Osmia bicolor
This record describes Osmia bicolor (species). Recorded family: Megachilidae. Recorded order: Hymenoptera.
Identification and Appearance

The female of this small (12 mm) bee is particularly attractive, with a black head and thorax and bright gingery hairs covering the abdomen. In the male the ginger is less striking. 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 Group . 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’. This is a bee that uses vacant snail-shells as nest sites. It uses masticated leaves to build up to five cells inside before camouflaging the shell with grass or dead leaves. Mainly found south of a line between The Wash and the Severn Estuary. No additional images available for this species.
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Hymenoptera
- Family
- Megachilidae
- Genus
- Osmia
Imported taxonomy record. Source availability varies; see the source references and editorial policy below.
Habitat and Range
Habitat
Various habitats.
Seasonal Activity
April to July.
Diet and Behavior
Life History
This is a bee that uses vacant snail-shells as nest sites. It uses masticated leaves to build up to five cells inside before camouflaging the shell with grass or dead leaves.
Additional species information
Recorded status
Mainly found south of a line between The Wash and the Severn Estuary.
About Flies: the wider group
Order-level background for Hymenoptera, the group containing Osmia bicolor. Species-specific details appear above.
Group overview
Hymenoptera includes over 150,000 described species of ants, bees, wasps, and sawflies. Earth harbors approximately 20 quadrillion (20×10^15) ants, with a combined biomass of ~12 megatons of dry carbon - exceeding the combined biomass of all wild birds and mammals (PNAS, 2022).
Ecological role of the group
About 35% of the world's food crops depend on animal pollinators. The chocolate industry, valued at over $100 billion, depends on pollinating flies and midges. Ants are the dominant soil engineers in most terrestrial ecosystems, turning more soil than earthworms in many habitats.
Economic and practical significance of the group
Pollinators contribute $235-577 billion worth of annual global food production (FAO). In the U.S., bee pollination alone benefits crops valued at $18 billion annually, and honey bees are responsible for $5.4 billion in agricultural productivity. Between April 2023-2024, 55.1% of managed honey bee colonies were lost. The U.S. bee population dropped from 5 million to 2.5 million.
Recorded sources for this group: FAO, USDA, EPA, PNAS (2022), US Fish & Wildlife Service. Imported estimates may describe particular regions or reporting periods.
Photos of Two-coloured Mason Bee (4)
Frequently Asked Questions About Two-coloured Mason Bee
What is Two-coloured Mason Bee?
Two-coloured Mason Bee (Osmia bicolor) is a species in the family Megachilidae, within the order Hymenoptera.
Where is Two-coloured Mason Bee found?
Habitat: Various habitats.
When is Two-coloured Mason Bee active?
Two-coloured Mason Bee: seasonal activity - April to July..
What is the life cycle of a Two-coloured Mason Bee?
This is a bee that uses vacant snail-shells as nest sites. It uses masticated leaves to build up to five cells inside before camouflaging the shell with grass or dead leaves.
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