out of the cocoons and through the mud plugs. The females, which are almost always in the inner cells of the tunnel, emerge several days later. One or two weeks may be required for all the bees to emerge during cool weather.
Females mate soon after emerging and begin nesting in 3 to 4 days. The bees forage on a number of different flowers. In wooded areas, they seem to prefer ballhead waterleaf. In urban areas, dandelion and Oregon grape are commonly visited, in addition to cherries and apples.
The mason bee is non-aggressive and will sting only if handled roughly or if it should get trapped under clothing. It is less objectionable than the honey bee as a pollinator in urban areas and should be encouraged. Efforts are being made experimentally to develop large populations of these bees to use as a supplement to honey bees for fruit pollination, much as the alfalfa leaf cutting bee was developed for alfalfa seed pollination.
Populations for pollinating around a home or commercial orchard can be developed by establishing trap nests to collect the bees. Trap nests can be made by drilling holes 1/4 to 3/8 inches in diameter and 3 to 6 inches deep in pine or fir 4x4's. A "brad-point bit" leaves a nice, smooth hole. (Figure 57) Alfalfa leaf cutting bee boards with hole diameters of at least 1/4 inch can also be used. These boards are then attached to a house or other structure where bees have been seen. Some protection from rain is desirable. Boards can also be placed on dead trees or posts in wooded areas near streams where there is a good supply of mud for nest construction and wild flowers on which to forage.
Predrilled Drilled Block Infested with Mason Bees. Image Courtesy of Red 58bill.
Boards should be positioned where they will receive morning sunlight and started in March before the bees begin nesting and remove them in early to mid-summer when nesting is completed. If the boards are stored outdoors over winter (under cover to protect them from rain and snow) the bees will usually emerge in March and April. The