The blue orchard bee (Osmia lignaria) is a solitary, early-spring pollinator known for its exceptional efficiency, visiting up to a thousand blooms daily. Unlike honeybees, these gentle insects do not form large colonies. Instead, each female constructs individual nests in small, pre-existing cavities. Mason bees are active for only four to six weeks in the spring, during which they mate, forage, and build nests. For the remainder of the year, they develop and hibernate inside protective cocoons, requiring year-round human intervention to ensure their survival and maintain a healthy local population.
Setting Up the Nesting Habitat
The nesting environment must be prepared before spring emergence to attract female bees. The bee house should face south or southeast to receive morning sunlight, which warms the bees and prepares them for flight. Secure the habitat against a flat surface, such as a wall or fence. It should also be placed under an eave or roof overhang to protect the nesting materials from wind and rain.
Successful long-term management requires using nesting materials that can be opened and cleaned, unlike simple drilled blocks or non-removable bamboo. Preferred options include removable paper tubes, reeds, or wooden nesting trays. These materials allow for the critical fall harvest necessary to remove pests and parasites. Nesting holes should be approximately 8 millimeters (5/16 inch) in diameter and at least 6 inches deep to encourage a healthy mix of male and female offspring.
Mason bees require two specific resources near the nesting site: early-blooming pollen and moist, clay-rich mud. Female bees use this mud as a mortar to construct the cell walls that separate each egg and pollen loaf within the nesting tube. If the native soil is too sandy, place a container of moist clay or a commercial mud mix within 10 to 20 feet of the house. Ensuring a variety of early spring flowers, such as fruit trees or dandelions, are blooming nearby guarantees a food source for the bees upon emergence.
Caring for Active Bees
The initial release of mason bee cocoons should be timed precisely to align with local flower blooming and consistent daytime temperatures. Place cocoons in the nesting house when the ambient temperature consistently reaches 55°F (13°C), which is the thermal threshold for flight activity. Males typically emerge a few days before the females, waiting to mate and begin the cycle of a new generation.
Once the bees are active, maintain the consistency of the mud source, ensuring it remains damp and workable, similar to modeling clay. Female bees will not nest if they cannot access this building material for their brood cells. Although the bees are generally docile, they are vulnerable to predators and parasites during the nesting phase. Monitoring the nesting tubes for signs of pests, such as small holes in the mud caps, protects the developing larvae.
As the season progresses, nesting activity slows, and females seal the tube entrances with a thick final mud cap. This usually occurs by early summer, around June, when the adult bees complete their short life cycle and die. At this point, remove the sealed nesting material from the outdoor habitat. Store it in a cool, protected location, such as a shed or garage, to shield the developing cocoons from heat, predators, and summer pests like the Houdini fly.
Harvesting and Cleaning Cocoons
Harvesting the cocoons is a step in the care cycle, typically performed in the fall, from September to November. This occurs after the larvae inside have fully metamorphosed into adult bees. The process begins by gently opening the nesting materials, such as peeling back paper inserts or separating wooden trays. Inside the tubes, healthy, brown, silk cocoons will be found alongside mud partitions, pollen mites, and frass (the fecal matter of the larvae).
The goal of harvesting is to separate healthy cocoons from debris, pests, and diseases like chalkbrood, a fungal infection. Cocoons are carefully extracted from the nesting chambers, often using a small, soft-tipped tool, and placed in a container for cleaning. Since cocoons are waterproof, they can be gently washed in a mild bleach solution (one teaspoon of bleach per cup of cool water). This sterilizes the silk from mites and chalkbrood spores.
During washing, lightly rub the cocoons between the fingers to remove stuck-on frass or mud, taking care not to squeeze the delicate adult bee inside. After a brief soak, rinse the cocoons in clean water. Then, spread them out to air dry completely for at least 30 minutes to prevent mold growth during storage. Discard any cocoons that appear amber, soft, or have holes from parasitic wasps immediately to avoid contaminating the healthy population.
Overwintering and Spring Emergence
Following cleaning, the healthy, dried cocoons must enter a period of controlled dormancy, or diapause, necessary for their survival and proper development. Place the cocoons in a ventilated container that maintains a specific humidity level. A small container with air holes, often lined with a slightly damp paper towel to prevent desiccation, is suitable for refrigeration.
The ideal storage temperature is consistently cool, between 34°F and 40°F (1°C and 4°C). This mimics natural winter conditions and ensures the bees conserve their energy reserves. Storing the cocoons in a standard household refrigerator is effective, but keep them away from ethylene-producing fruits that could disrupt their dormancy. This chilling period fulfills their cold-hour requirement, allowing the adult bees to remain in a low-metabolic state until spring.
The final step is timing the re-release of the overwintered cocoons back into the prepared habitat. When spring arrives and daytime temperatures reach the 55°F threshold, the cocoons are ready to be placed outside. Set them in a small, protected chamber within the bee house to allow them to emerge naturally and begin the pollination cycle anew.