Blue Orchard Mason Bee

Osmia lignaria — the blue orchard mason bee — is one of about 4,000 species in family Megachilidae and one of the most ecologically and agriculturally important pollinators in temperate North America. The species is solitary (no colonies, no queens, no workers): each adult female builds her own nest. Females search for pre-existing cavities (woodpecker holes, hollow stems, beetle borings, or commercial nest tubes) and partition the tube into individual brood cells. Each cell receives an egg, a pollen-and-nectar provision, and is sealed with a mud wall constructed from clay or moist soil — the source of the 'mason' common name. Mason bees are exceptionally efficient pollinators because they are 'belly-flop' pollinators: they carry pollen on the underside of the abdomen rather than in pollen baskets like honey bees, and the pollen is loosely held — meaning they shed it abundantly onto each flower they visit. A single female mason bee pollinates as many fruit blossoms in a day as 100 honey bee workers. The species is native to North America, gentle (males are stingless; females sting only when squeezed), and increasingly used as a managed pollinator in commercial orchards as a hedge against honey bee colony collapse. The flight season is short (4-6 weeks in spring), corresponding precisely with fruit-tree bloom.