Osmia lignaria, commonly known as the blue orchard bee or mason bee, is a solitary bee species found in North America. They are known for their metallic blue-black coloration and robust build. These bees are important pollinators, particularly for fruit trees and orchard crops, making them valuable for agricultural purposes. Osmia lignaria constructs nests in pre-existing cavities, such as hollow plant stems or woodpecker holes, using mud or plant material to create individual cells for their eggs.