The Red Mason Bee (Osmia bicornis) is a solitary bee species, characterised by its dense gingery-red hairs, making it a distinctive native spring flying bee. Males have a white tuft on their heads, while the females have a black head with two “horns”. It is an important early-season pollinator, particularly efficient for pollinating fruit trees. In Scotland, this solitary bee is present but rarer and more localised compared to England and Wales, where it is widespread and common.
This bee is known for its above ground nesting behaviour nests, utilising pre-existing holes or cavities such as hollow plant stems, bamboo, air bricks, old nail holes and holes in masonry and can be easily coaxed into made and bought ‘bug hotels’.
The Red Mason Bee is polylectic forager, meaning it forages pollen from various early-spring flowering plants, making it a valuable pollinator for orchards, gardens and wild habitats. The pollination efficiency of this solitary bee species surpasses that of honeybees for early blooms, as it forages effectively at lower temperatures (around 10-15°C).
Rather than collecting pollen and transporting it on their legs like many other bees, Red Mason Bee females (along with other Osmia species) collect pollen in hairs on the undersides of their abdomen, in a structure known as a “pollen brush”. When the pollen brush is full, the underside of the bee can look very bright and vibrant, depending on the colour of the pollen collected.
Photo: Tonstudio96, (CC BY – SA 4.0)
Action Needed
- Support the inclusion of a legally binding target on habitat connectivity under the Natural Environmental Act.
- Champion B-Lines as a solution to reversing habitat loss and insect decline.
- Commit to B-Lines being used by the Scottish Government to target wildflower habitat restoration delivering Nature Networks.
- Support sustainable farming, including wildflower habitat restoration and creation in the Rural Support Plan 2026-2030.
- Ask Parliamentary Questions on insect loss and habitat fragmentation to continue pressure on the government to follow through with their promises.
Threats
Climate change poses significant threats to Osmia bicornis populations through altered overwintering conditions. Warmer winter temperatures increase overwintering mortality, and projected warm spells bring forward emergence timing of the bees, resulting in a mismatch between the emerging bees and the flowers that they need to feed upon.
Habitat loss and fragmentation – Agricultural intensification, land-use changes and pressure for new development, continue to threaten wildflower-rich habitats like meadows, grasslands and hedgerows at an alarming rate. Over 97% of the UK’s wildflower-rich grasslands have been lost since the 1930s. These vital areas where insects can thrive have shrunk into tiny, scattered fragments, leaving pollinators unable to move through the landscape, colonise new areas or respond to threats like climate change. B-Lines is a national effort to create and restore habitats for pollinators as a solution to our pollinator crisis.
MSP Nature Champion
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