Ground Nesting Bees – What to Look for and What Species to Expect
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Collapse ▲What to Look for
Out of the more than 20,000 bee species in the world, approximately 70% build their nests underground. Females of these species lay their eggs in underground nests; the young then develop into the next generation of adults in these nests. Some of these species nest in what are called aggregations. These bees typically have very specific requirements for nesting substrates and conditions which results in many individuals nesting in close proximity to each other within the areas that meet those requirements. These species tend to nest in the same location year after year resulting in increases in size and nest density each year, sometimes resulting in thousands of nests.
In North Carolina, there are 5 genera that commonly nest in aggregations (approximately 212 species total): Andrena, Anthophora, Colletes, Habropoda, and Lasioglossum. These species can be active at different times across the year and provide important pollination services to various plant species. For more details see The Bees of North Carolina: An Identification Guide.
These nests can be mistaken for other insect nests and care should be taken to identify nest occupants before any removal actions are taken. These bee species are important pollinators for wild plants and crops. To help support bees, both nesting habitat and forage habitat should be protected whenever possible. For early spring species foraging habitat includes plant species such as red maples, redbuds, blueberries, apples, willows, and cherry blossoms; while for fall species this includes plant species such as goldenrods and asters.
Left: image of a ground nesting bee emerging from a ground nest entrance. Right: image of a large ground nesting bee aggregation. Nest entrances are mounds of soil with an emergence/entrance hole in the middle. Photos by Hannah Levenson.
What Species to Expect
Andrena
Also known as mining bees, Andrena is the most species-rich genus in North Carolina. They are the most noticeable early spring nesting species with peak adult activity between March and May (see activity period below), but, depending on the species, activity can occur anytime from February through October. Species in this genus are typically among the first ground nesting species people notice each year and are known for forming very large aggregations.
Image of Andrena barbara from the USGS Bee Lab’s Flickr page.
Body size
Andrena are small bodied bees with the largest individuals smaller than a penny.
Image from The Bees of North Carolina.
Activity period
Peak activity is expected between March and May for this genus, but can occur between February and October for some species.
Image from The Bees of North Carolina.
Anthophora
Also known as digger bees, Anthophora can be easily mistaken for bumble bees. The easiest way to tell them apart is by looking at their pollen collecting hairs – bumble bees have pollen baskets where digger bees have hair all over their hind legs. These bees usually form turrets at their nest entrances (see image below). Nests are often found in clay soils, cob structures, and even clay pizza ovens.
Image of Anthophora abrupta from the USGS Bee Lab’s Flickr page.
Anthophora nesting aggregation. Image by Hannah Levenson.
Body size
Anthophora can be about the size of a penny, or smaller. Their bodies are round in shape and they can be mistaken for bumble bees.
Image from The Bees of North Carolina.
Activity period
Flight activity can occur between March and November, with peak activity occurring in June.
Image from The Bees of North Carolina.
Colletes
Also known as cellophane bees, Colletes waterproof their nests with a cellophane-like substance. Species in this genus can also form large aggregations in the early spring, but many species are active in the fall.
Image of Colletes inaequalis from the USGS Bee Lab’s Flickr page.
Body size
Colletes are small, similar in size to Andrena, with the largest individuals smaller than a penny.
Image from The Bees of North Carolina.
Activity period
Activity for this genus can occur between March and October. Many species are active in the spring (March – April) while others are active in the fall.
Image from The Bees of North Carolina.
Habropoda
There is only one Habropoda species in North Carolina, Habropoda laboriosa. This species is also known as the southeastern blueberry bee and is an economically important, specialist pollinator on blueberries. Habropoda can also easily be mistaken for bumble bees, however, just like with Anthophora the easiest way to tell them apart is by looking at their pollen collecting hairs – bumble bees have pollen baskets where Habropoda have hair all over their hind legs. With this in mind, Habropoda and Anthophora can look very similar, but are active at different times of the year with Habropoda active earlier.
Image of Habropoda laboriosa from the USGS Bee Lab’s Flickr page.
Body size
Habropoda can be about the size of a penny, or smaller, with very rounded bodies.
Image from The Bees of North Carolina.
Activity period
Flight activity can occur between March and November, with peak activity occurring in April when blueberries, and other related species, bloom.
Image from The Bees of North Carolina.
Lasioglossum
Also known as sweat bees, Lasioglossum is a very diverse genus with many species being very difficult to identify. Depending on the species, they can be black or a dull metallic color.
Image of Lasioglossum versatum from the USGS Bee Lab’s Flickr page.
Body size
Lasioglossum are known for having small body sizes with most species much smaller than a penny.
Image from The Bees of North Carolina.
Activity period
Image from The Bees of North Carolina.
Peak activity is expected between March and December for this genus, with peak activity expected in the summer and early fall.