Entomologist’s tips for installing and maintaining native bee 'houses'

Bee boxes, often called bee “houses” or “hotels,” offer an opportunity to learn about Virginia’s solitary bees while helping pollinators. However, if constructed improperly or neglected after installation, these habitats can actually be harmful to solitary bees.

Unlike the familiar hive-forming honey bee, solitary bees don’t live together in colonies. Instead, individual female bees build their nests alone.

Virginia has dozens of species of solitary bees, including different kinds of mason bees and leafcutter bees, which use small cavities to construct nests made of mud or leaves. Commercial and homemade bee boxes that contain tubes made from natural reeds or cardboard straws can give these bees a safe place to lay their eggs.

When constructed and maintained properly, bee boxes offer an excellent opportunity to see solitary bees up close.

“Don’t be afraid of these bees,” said Tim McCoy, a Virginia Cooperative Extension associate with Virginia Tech Pesticide Programs. “They’re not aggressive and they really have no interest in humans. Bee boxes are an easy way to learn and have a chance to watch them.

"When buying or making a bee box, the first thing is to look for one with nesting tubes that are 5 to 6 inches long,” McCoy said. “Different types of bees will use different diameter tubes, but they need to be between three-thirty-seconds of an inch and three-eighths of an inch in diameter.

“I’ve seen houses for sale with bamboo tubes that are only a few inches long,” said McCoy. “Bees will spend time investigating those houses, but they ultimately may not use them, so it can be a waste of their time.”

According to McCoy, bee boxes should be installed in a location that will receive full morning sun; is within 100 to 200 yards of a pollen source; and is within 50 yards of a source of mud, which some bee use to construct their nests. In the winter, boxes should ideally be stored in an outbuilding that gets atmospheric temperature, or in an outdoor location sheltered from the elements. The following spring, the tubes can be placed outside, when temperatures are above 55 degrees, so the bees can emerge.

Importantly, nesting tubes need to be replaced each year after bees emerge, otherwise they can harbor disease and parasites.

“I recommend against the types of bee houses made by drilling holes in a block of wood,” said McCoy. “It’s just too labor intensive to drill a 6-inch hole, and you’re not really making an ideal nest for the bees.”

McCoy also recommends against trying to clean out used nesting tubes — a task difficult to do well enough to effectively remove pathogens. Instead, McCoy recommends a house with natural reeds or cardboard tubes which can be replaced each year after the bees emerge.

Bee houses constructed so that nesting tubes cannot be removed and replaced will need to be discarded after one use.

For installing your own bee box, McCoy recommends:

• Choose a location with full morning sun.
• Make sure your location is within 100 to 200 yards of a pollen source and within 50 yards of a mud source.
• As bees emerge in spring, consider protecting the nest so the bees can get out but squirrels and birds can’t get in. For example hardware cloth can be affixed over the front of the nest to allow bees to safely emerge.
• Store the nest over the winter in an outbuilding that will get atmospheric temperatures.
• Make sure your habitat’s tubes are at least 5 to 6 inches long with diameters from three-thirty-seconds of an inch to three-eighths of an inch (mason bees favor tubes five-sixteenths of an inch in diameter).
• Wait until your bees emerge each year and replace used tubes. (Cardboard or natural reed replacement tubes can be purchased online.)

The mason bees and leafcutter bees who might nest in bee boxes emerge in spring and summer and will live for only one season, during which time female bees build nests and lay their eggs. Female bees leave pollen and one egg in individual cells they construct in the tube. Each cell is sealed off from the other as the tube is filled. Finally, the bee closes the tube with mud (mason bees) or leaf material (leafcutter bees). The egg within each cell, becomes a larva, eats its pollen, and spins a cocoon. The adult bee remains dormant within its cocoon until spring temperatures are warm enough for them to emerge.

For Virginians interested in making a thorough study of the bees visiting their area, McCoy recommends the book "The Bees in Your Backyard: A Guide to North America's Bees," by Joseph S. Wilson and  Olivia J. Messinger Carril.

For more information on Virginia’s native bees, see this Virginia Cooperative Extension Publication.

Interested in learning more about gardening? Virginia Cooperative Extension Master Gardeners can help! Master Gardeners bring the resources of Virginia’s land-grant universities – Virginia Tech and Virginia State University – to the people of the commonwealth. Contact your local Master Gardeners through your Extension office or click here to learn more about gardening in Virginia and the Virginia Extension Master Gardener program.

—Written by Devon Johnson