Red mason bee ♂︎ -Ranunculus acris- Last update: 30 November 2019 Common OBSERVATION:2016-V-28 A male Red mason bee (Osmia bicornis, synonym Osmia Rufa) on Meadow buttercup (Ranunculus acris). Red mason bee ♀︎ (Osmia rufa / Osmia bicornis) on Meadow buttercup (Ranunculus acris)