Bees of the Andrena genus are more commonly referred to as “Mining Bees,” and they differ from other types of bees because of their ground-nesting habits and weak stingers.
The Xerces Society, a nonprofit conservation organization, is a leader in the effort to conserve North America's native pollinators. Founded in 1971, the society protects insects and other invertebrates through advocacy, education, policy development and applied research projects aimed at protecting and managing critical habitat. Attracting Native Pollinators (Storey Publishing, 2011), by The Xerces Society, is a complete action plan and information guide for protecting bees, wasps, butterflies, moths, flies and some beetles by providing flowering habitat and nesting sites.The following excerpt comes from Part 3: Bees of North America.
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Andrena are frequently encountered by gardeners because of their ground nesting habits in lawns. This is a large and diverse genus with nearly 1,500 species worldwide, and about 400 in North America. Though they are found in all types of habitat, Andrena are much more common in temperate than tropical regions.
Small to moderate-sized bees, 0.3 to 0.7 inches (7–18 mm) long. Most North American Andrena species are black, dull metallic blue, or green and moderately hairy, with bands of pale hair on their abdomens. Females have large, velvety facial depressions (foveae) that look like eyebrows and large pollen-collecting hairs (scopae) on the upper part of their hind legs, seemingly in their “armpits.” Despite a variety of striking colorations, Andrena species are difficult to tell apart.
Similar Types of Bees
Colletes and Halictus can be a similar size and color, but the lack of stripes on the abdomen of the Mining Bee makes it straightforward to separate them.
In the western United States, Mining Bees are among the most common types of bees that forage in the spring, with some species emerging as early as February. The genus contains both species that visit a wide variety of flowers and specialists.
All Andrena nest in the ground, typically in sandy soil and often near or under shrubs. The nest entrance is usually marked by a small mound (tumulus) of soil. The female lines her brood cells with a material she secretes from a specialized gland. Unlike Colletes, the secretion of Andrena soaks into the soil. It dries and is rubbed by the female using a flat area near the tip of her abdomen (the pygidial plate) to form a highly polished and stable cell wall.
Many Andrena species nest in large aggregations of tens of thousands of bees. Even within such a large gathering, the individual bees are solitary, though nests can be in densities of 30 entrances per square foot. A few species nest communally, where two or more females share a nest entrance but build and provision their own brood cells.
Several Andrena species are considered vulnerable or imperiled. A. aculeata and A. winnemuccana are on the Xerces Society’s Red List, though little is known about their biology. Both are limited to the Columbia River basin. Only one specimen of A. winnemuccana has been collected, and both species may be threatened by habitat loss. Several Andrena species from California and Nevada are listed as critically imperiled or imperiled on the NatureServe Explorer database.
Did You Know?
Mining Bees regularly nest in lawns, especially in spring, but, unlike other types of bees, pose no risk to people because their weak stingers cannot penetrate human skin.
To learn more about mining bees and other types of native pollinators, read How to Attract Native Bees to Your Organic Garden.
"Bee" an expert! Identify more types of bees from Attracting Native Pollinators
Regional Plant Lists for Native Pollinator Gardens
The following charts list plant species that are native to their respective regions and commercially available from nurseries, specialty seed producers, and local native plant societies. The plants listed here tolerate a wide range of soil and light conditions. They are listed by season, to make it easier to design a garden that provides forage in spring, summer, and fall. If particular species are difficult to find in your area, look for closely related ones.
Northeastern United States and Eastern Canada
Southeastern United States
Midwestern United States
Great Plains and Prairie Provinces
U.S. and Canadian Rocky Mountain Region
California and the Southwest
Pacific Northwest and British Columbia
Lower-Cost Ornamentals for Many Regions
This excerpt has been reprinted with permission from Attracting Native Pollinators: Protecting North America's Bees and Butterflies by The Xerces Society, published by Storey Publishing, 2011. Buy this book from our store: Attracting Native Pollinators.