Nest-building in empty snail shells — Mason bee ecology elucidated by Kindai University and University of Tsukuba

A research group led by Associate Professor Ikuo Kandori of the Department of Agricultural Science, Faculty of Agriculture, Kindai University, in collaboration with Assistant Professor Tomoyuki Yokoi of the Institute of Life and Environmental Sciences, the University of Tsukuba, has announced the elucidation of the ecology of Osmia orientalis, a mason bee that builds nests in empty snail shells. The study revealed the species' preferences for specific types of empty shells needed for nesting and surrounding environmental conditions. The pollination efficiency of O. orientalis was found to be equal to or greater than that of the western honeybee (Apis mellifera), indicating potential for use as a pollinator in agricultural settings. The group's findings were published in the international academic journal Insects on April 29.

The western honeybee is utilized worldwide as a pollinator for agricultural production and is used in Japan for crops such as apples, watermelons, strawberries, and melons. However, western honeybees have the disadvantage of avoiding certain plant flowers, resulting in low pollination efficiency for some crops. Furthermore, western honeybees are an introduced species in Japan, raising concerns about their impact on ecosystems.

In contrast, attention is being focused on utilizing mason bees, native bee species, with research advancing on their ecology and pollination capabilities. Many mason bee species are known to build nests in bamboo tubes, tree holes, or underground, and some species build nests in empty snail shells.

The research group therefore focused on O. orientalis, the only mason bee species distributed naturally in Japan that builds nests in snail shells. To verify the agricultural potential of this mason bee, they conducted three experiments.

First, to clarify nesting preferences, they placed snail shells from four species-Euhadra amaliae, Satsuma japonica, Sinotaia quadrata histrica, and Helix lucorum-in six different environments and investigated which shells in which environments the bees would choose. Results showed particularly high nesting rates in shells of the medium-sized snail Euhadra amaliae and revealed that the bees prefer grassland environments for nesting. They did not favor bare ground or forest interiors.

Next, the group investigated the pollination efficiency when O. orientalis visited strawberry flowers. Results showed that pollination efficiency was equal to or greater than that of western honeybees, which are commonly used for strawberry pollination. Furthermore, they CT-scanned empty E. amaliae shells and used 3D printers to create four types of plastic artificial shells (nylon, acrylic, polypropylene, ABS) that accurately replicated the internal structure. These were placed in greenhouses alongside E. amaliae shells to compare nesting rates. Results showed that three types of artificial shells (excluding ABS) had nearly the same nesting rates as E. amaliae shells.

Looking forward to future agricultural applications

Kandori commented: "I initially thought it was interesting that there was a bee with the unique behavior of building nests in empty snail shells and started research by investigating this bee's nest-building behavior. Eventually, I began thinking that since we had elucidated these behaviors, we should try to find ways to use this knowledge for agricultural applications, leading us to the idea of using artificial plastic shells as nesting materials. I would like to continue developing this research, dreaming of the day when this bee will be used in agriculture."

Journal Information
Publication: Insects
Title: Nesting Preferences of Osmia orientalis (Hymenoptera: Megachilidae) in the Field and Its Potential as a Strawberry Pollinator in Greenhouses
DOI: 10.3390/insects16050473