There are so many more bees beyond honey bees: It’s time to show our native bees some love!
Did you know that there are over 20,000 recognized species of bees around the world, 4,000 of which are native to the United States? Although pollinator protection efforts have been a core focus in ecological stewardship, most of us tend to focus on the European honey bee (Apis mellifera) and miss out on the bulk of the wonderfully diverse pollinator populations found across the globe.
The European honey bee has long been used as the surrogate species for both Apis and non-Apis bees and other insect pollinators in risk assessments. The focus on A. mellifera makes sense for a few reasons: (1) we have a strong understanding of its behavior and ecology, (2) A. mellifera have a long history of management for honey production and, more recently, crop pollination, and (3) this species is commercially available and relatively easy to keep under laboratory conditions.
Focusing on the European honey bee has its drawbacks. For example, the protection goals set forth in the 2014 Guidance for Assessing Pesticide Risk to Bees by the USEPA, Health Canada and the California Department of Pesticide Regulation, including maintenance of pollination services, hive production, and biodiversity, do not uniformly apply to both Apis and non-Apis bees. In other words, thousands of non-Apis bee species may not benefit from protective efforts set forth by these guidelines and could be at a potential risk from pesticides. Bee species are diverse in life cycle, sociality, nesting and foraging behavior, overwintering, and size and their diverse ecology and behavior should be accounted for when considering risk from chemical exposure and toxic effects.
While the European honey bee receives most of the credit, many species are very important for crop pollination—and few of them are managed for this purpose. In many cases, non-Apis bees turn out to be more effective pollinators than the honey bee, such as:
Bumble bees (Bombus ssp.) are relatively large in size as well as furry in comparison to many other bees, allowing them to pick up and carry more pollen from plant to plant. They are social bees, but with only a few hundred worker bees, their colonies are much smaller than European honey bee colonies. Bumble bee colonies do not overwinter. Instead, mated queens overwinter and start a new colony on their own in the spring. Bumble bee species are commercially available for crop pollination in North America, Europe, and Asia.
Not all bees live in colonies! Solitary bees comprise a vast variety of bee species that, in turn, employ various nesting strategies. A few of these solitary bee species can be managed for crop pollination, most prominently species in the genus Osmia: blue orchard bees and the red mason bees are used in orchard pollination, and the leaf-cutting bee, Megachile rotundata, is managed for alfalfa pollination. These three species nest in above-ground, existing cavities, making it relatively easy to provide artificial nesting sites and collect the overwintering bees that have not emerged from their cocoons yet.
However, the majority of bee species nest underground, usually digging their own nests. Examples include the following bees: the squash bee (Eucera pruinosa) which exclusively forages for the pollen of plants in the cucurbit family and the alkalibee (Nomia melanderi), an avid pollinator of alfalfa. The alkali bee is found in the Western United States and nests in soils with high salt content. It can form large nest aggregations in suitable locations and farmers may set aside and manage areas close to their alfalfa fields to create the right nesting conditions for the bees.
In tropical regions, including for instance Brazil, stingless bees (Meliponini) are considered key pollinators. Like the honey bee, they are highly social and live in large colonies. They comprise a variety of species across the globe with a large diversity in ecology, nest architecture, and substrates used for nest building.
In order to consider the potential impacts of chemicals to the wide variety of bees, we must acknowledge the different routes of exposure. Dependent on the species and its ecology, bees can come into direct contact with chemicals through dust or spray, mud and soil, nesting materials (e.g., wax or leaf pieces), plant surfaces and plant resins. In addition, bees can also be exposed orally to residues in nectar and pollen. Exposure will also vary depending on life-stage and, in social bees, castes. Beyond the exposure routes, bee physiology can result in different sensitivities to toxic compounds across bee species. As you can see, bees can vary greatly in biological and behavioral characteristics and research is needed to better understand the interaction between these characteristics and the potential pesticide exposure and effects at the level of a colony or population. Recently, we have been working to apply a trait-based vulnerability assessment across 10 different bee species with individual and population-level implications. We’re looking forward to publishing our findings soon. Stay tuned to our upcoming newsletters for more on this important work. In the meantime, we encourage you to explore the various bee species native to your area. The Xerces Society has a multitude of educational resources if you’d like to learn more about the diverse pollinators in your region.