14 Blue Orchard Mason Bee

Osmia lignaria

Characteristics

Length: 0.39–0.47 in (10–12 mm).

Flight season: March–May.

Nectar sources: Fruit trees.

Habitat: Forest edge, farmland, grassland, gardens.

Native to North America, blue orchard mason bees have a metallic, greenish-blue head, thorax, and abdomen. They are exceptional pollinators of fruit trees early in spring. For this reason, they are managed by orchard farmers, who place “bee hotels” made from wooden tubes or simply drill holes in wood near the apples, pears, plums, cherries, peaches, or almonds they want the bees to pollinate. Since these bees don’t fly far for their pollen, this is a good way of enticing them to stay close to the orchard.

The males emerge first, feeding and waiting for females to take to the wing. After bee couples have mated, the females go in search of suitable nest holes. Unlike carpenter bees, they can’t excavate their own burrows, so they depend on natural cavities—or those put out for them by farmers. A mixture of pollen, nectar, and saliva is rolled into a food ball at the farthest section of the hole, an egg is laid on it, and a cell is sealed with a mud partition. The female builds five to eight cells in the cavity and goes off to do the same again. She may fill several burrows with eggs before she dies. Inside, the eggs hatch, the grubs eat the food ball, and eventually change into pupae—to emerge the following spring as the next generation.