Reduce over-wintering losses from predators and very warm and very cold winter days, by storing your tubes through the winter months in a refrigerator or in an unheated, insulated shed, shop, or garage.
Place rubber-banded bundles of tubes (with openings pointing upwards or horizontal) inside these zippered protective bags, in the fall, before any hard freezes occur. For best results, store the bags in a refrigerator, which keeps the larvae cool but protected from freezes. In milder climates, like the Pacific Northwest, the bags can also be used in an unheated, insulated outbuilding, which doesn’t get too warm. Warmth may trigger early development of the larvae, leading to premature emergence and loss of your young mason bees.