Feature
Bee H o te ls
or Bates Motels? The Need for Research in Guiding Pollinator Conservation Efforts By Dr. Jennifer Tsuruda, Assistant Professor, UT Entomology and Plant Pathology Department, and Dr. Laura Russo, Assistant Professor, UT Ecology and Evolutionary Biology Department
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A “Bee Hotel” is constructed with human-sourced or modified nesting aids that are designed for solitary stem-nesters such as leafcutter bees and mason bees [Photo 3]. These types of solitary bees are highly valuable pollinators in agricultural, urban, and natural landscapes [Photo 4]. Bee hotels [Photo 5] are commonly built as bundles of tubes or in the form of a wooden block with horizontal, drilled holes. Holes do not penetrate all the way through the back side of the block. When tubular stems are used, one end of each within a stem bundle is cut below the nodes so there is only one open end. When cardboard or paper straws are used, they are folded so that only one end is open. Stems, tubes, or paper straws are then tightly strapped or packed together in a protective “house” structure and positioned horizontal to the ground. Nest designs and characteristics can influence the utilization by certain bees. For example, small cellophane bees will utilize nests with 1–4 mm diameter holes, whereas mason and leafcutter bees are more likely to use holes with 5–8 mm diameters1 [Photo 3]. Additionally, a study on mason bees showed that more females were provisioned in a light blue nest box versus yellow or orange-colored boxes. Nest box placement can also influence colonization and success. Blocks and bundles are often housed within a structure or stand that has an overhang at the top, which helps protect from rain [Photo 5]. These larger structures should be placed in a location with limited wind exposure, facing south or southeast, and secured to prevent movement and risk of tipping over. Chicken wire or other wire mesh placed in front of the tunnels can help prevent predation by birds and small mammals.
ublic awareness about the decline of bees and other pollinators in recent years has been impressive and ever-growing. Pollinators have a tremendous impact on the day-to-day lives of humans. About one-third of the food we eat has been directly influenced by the activities of animal pollinators, so the concerns of scientists and the public are understandable. Growing awareness about these problems is often accompanied by a desire to act and help conserve pollinators in our landscapes and production areas. The inputs from citizen action can outpace science-based predictions and recommendations and a good example involves bee hotels and native bee conservation.
What is a bee hotel? Many people are familiar with social bees like honey bees and bumble bees. Less familiar are solitary bees that actually make up the majority of the ~3,500 native bee species found in North America. Rather than living within the same in colony structure, individual female solitary bees construct their own nest, sometimes adjacent to other solitary bee nests, yet each female provisions her own young without help from other bees, hence their “solitary” status. Approximately 70% of solitary bee species nest in the ground, while 30% nest above-ground in cavities such as stems, twigs, and abandoned tunnels in wood made by other insects. These cavities consist of a series of chambers, each provisioned with a ball of pollen mixed with nectar, and a single egg [Photo 1]. Chambers are sectioned off with partitioning material that varies with the type of bee – for example, leafcutter bees use chewed leaf tissue to separate chambers from one another [Photo 2]. After hatching from the egg, the larva consumes the founding female bee’s provisions and develops through multiple juvenile stages before pupating and emerging as an adult and leaving the nest.
An inhabited tube or nesting cavity may contain one or a series of cells, each containing a single egg that is provisioned with a ball of pollen mixed with nectar. Cells can be sectioned off from each other with a partition made of mud, leaf or petal tissue, resin, chewed up wood pulp, or even ants (photo by C. D. Pless and G. Schweiger).
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tennessee greentimes SUMMER 2022
By providing hollow stems with different diameters, and that are sealed at one end, a greater diversity of bees can occupy the bee hotel. Different species of bees and wasps require different materials to separate and seal their nesting tunnels. Here, chewed up green leaf tissue, dried grass, and mud seals can be seen, along with a returning leafcutter bee with leaf tissue in her mandibles (photo by Laura Russo).
