Six years after having started with specific forest management (ringcutting pine trees on the southfacing side) Osmia parietina was signaled in the Amsterdam Waterleiding dunes. This is the second observation in this area and the seventh in total since 1980. The long-horned beetle Rhagium inquisitor was also found at ths location. Is there a relation between the presence of the mason bee and the long-horned beetle?