Red Mason Bee

Fast Facts

Latin name: Osmia bicornis

Notable feature: Both males and females are covered in dense gingery colored hairs; males have a white tuft on their heads, while the females head is black with two “horns”.

Conservation Status: Not Evaluated

Where in the UK: Widespread in England and Wales, but rarer in Scotland and Northern Ireland.

Red Mason Bee (Osmia bicornis) © Steven Falk

The Red Mason Bee (Osmia bicornis) is a small but distinctive, native spring flying bee.  Both males and females are covered in dense gingery colored hairs; males have a white tuft on their heads, while the females head is black with two “horns”.

It is a solitary bee that nests in 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, meaning it forages pollen from various different flowering plants.

Rather than collecting pollen and transporting it on their legs like many other bees, Red Mason 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.

    • Size:  6-11mm in length, males tend to be smaller in size than females
    • Life span:  Annual life cycle. Eggs hatch after about one week; the larvae start spinning a cocoon about one month after hatching. The bees become adults in autumn, but stay dormant until the following spring. Upon emergence adults are thought to fly for around 8 weeks, completing their reproductive cycle and ensuring the next generation in the following year.
    • Diet:  The Red Mason Bee feeds solely on pollen and nectar. Peak activity matches the flowering period of the mass-flowering fruit trees such as Apple and Pear, ie late April to mid-May
    • Reproduction: Females will only mate once, usually with closely related males. After mating, each female builds its own nest; she lines each ‘cell’ with mud and pollen and lays a single egg in each until the cavity is full. The larvae hatch and develop, pupating in autumn and hibernating over winter.
    • When to see:  The Red Mason Bee is active from early Spring, with the males being first to appear and the females emerging slightly later.  Seen from April (sometimes late March) to June.
    • Population Trend:  Unknown. Widespread across the UK/Common.  IUCN Least Concern in Europe; Not evaluated globally
    • Threats: Loss of flower and species-rich habitat that provides important forage for the adult bees; re-mortaring of old walls, for example in churchyards, removing potential nest sites. Habitat fragmentation
    • Fun Fact:  Osmia bicornis is the current scientific name for this bee, although it was formerly known as Osmia rufa.  In 1758, Linnaeus described the male of this species under the name Apis rufa and described the female as a separate species Apis bicornis. In 1802 Kirby recognised that Apis bicornis and Apis rufa were the same species and he named this species Apis bicornis.

How you can help: 

Buglife is working to increase awareness of invertebrates and the Red Mason Bee through specific projects, including B-Lines, but we need your help!

Buglife B-Lines are an imaginative and beautiful solution to the problem of the loss of flowers and pollinators. B-Lines are a series of ‘insect pathways’ running through our countryside and towns, along which we are restoring and creating a series of wildflower-rich habitat stepping stones. Linking existing wildlife areas together, creating a network, like a railway, that will weave across the UK landscape.  More information about B-Lines and how you can help pollinators can be found on our B-Lines & Pollinator Projects pages.

Join a recording scheme and log your finds – send any records/sightings to BWARS or download the iRecord app and get recording!

Patrick Harvie MSP - Red Mason Bee Nature Champion
Patrick Harvie MSP – Red Mason Bee Nature Champion

Red Mason Bee Nature Champion:

Patrick Harvie MSP

  • Member for: Glasgow
  • Region: Glasgow
  • Party: Scottish Green Party

Find out more about Scottish Nature Champions

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