Mason Bee, common name for solitary bees that build part or all of their nests with mud.  They construct mud partitions between a linear series of brood cells (compartments for the larvae) that are produced in soil, hollow plant stems, or preexisting cavities, including wood laminates.Most mason bees are smaller than honey bees.. They have stout bodies, and are bluish in color. Mason bees are common in the western United States, especially in forested regions, but they are also found in many other parts of the northern hemisphere. About 140 species of mason bees are found in North America out of about 200 species worldwide. These bees have a sting but do not attack defensively unless handled. 

The orchard mason bee, or blue orchard bee, is a metallic blue-black species about 13 mm (0.5 in) long. This bee, native to North America, specializes in collecting pollen from the flowers of fruit trees. In some parts of the United States, the bees are cultivated to pollinate orchard crops, especially apples, cherries, and almonds. This bee nests in holes in wood and the females prefer to make nests close to each other in aggregations. These traits are used to concentrate enough bees in an area for commercial pollination. Blocks of laminated wood with holes in them attract nesting bees. These nest blocks are hung from trees or are placed in shelters for protection from the weather. 

Orchard mason bees mate in the spring. The females then begin to collect pollen and lay eggs. Larval bees feed for several weeks inside their closed cells. They pupate in late summer and spend the autumn and winter as adults inside their pupal cocoons in the nest. They emerge from the cocoons in the spring, coinciding with flowering of many orchard crops. The new generation of bees then begins the cycle over again. Orchard mason bees are very effective pollinators. Two or three females can pollinate the equivalent of a mature apple tree in one season. They fly in cool or rainy weather and can supplement or replace honey bees as commercial pollinators in some situations. 

Leafcutter Bees

Leafcutting bees are black bees with white or silvery hairs, and the top of the abdomen may have fine bands of white hairs. The underside of the female's abdomen has a dense brush of hairs that is used for carrying pollen. Males are usually smaller and in many species they have hairier faces than females. The bees range in size from small to moderately large, usually 1 to 2 cm (0.4 to 0.8 in) long. The alfalfa leafcutting bee was introduced into the United States from western Asia in the late 1930s for the commercial pollination of alfalfa plants. This bee is specially adapted for foraging on alfalfa flowers, which honey bees tend to avoid. These small flowers must be pried open by the pollinating insect, which then gets dusted with pollen by the flower's spring-loaded anthers. 

The alfalfa leafcutting bee is managed intensively for alfalfa pollination in Washington, Oregon, California, Idaho, and Montana. Production of the bees is a multimillion dollar business in the United States and Canada, and it is also important in Russia. Each female alfalfa leafcutting bee uses about 15 leaf or petal pieces to construct a brood cell (compartment for young). The bee stocks the cell with pollen and nectar, lays an egg on the pollen, and then seals the cell, leaving the larva to grow and develop into an adult bee. A linear series of such cells is produced in a nest hole 6 to 8 mm (0.25 to 0.31 in) in diameter. Each female may produce up to 40 offspring, but usually produces about 12 to 16. Most nests are made in the spring and the subsequent generation does not emerge until the spring of the following year. However, some females emerge after only a few weeks and make a second generation of nests in the same summer. Alfalfa leafcutting bees are parasitized by fungi, other bees, and wasps. Watts Solitary Bees has been raising alfalfa leafcutter bees for 50 years.  We provide bees to farmers for pollination in their crops.