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Animal

Mining bee

Andrena spp.

Also known as: Andrena bees, Digger bee

Solitary ground-nesting native bees, ~450 species in North America — the largest single bee genus on the continent. Females excavate vertical burrows in bare or sparsely-vegetated soil, leaving small mounds of excavated earth at the entrance. Active in early spring when soils warm; many species are specialists on willows, fruit trees, blueberries, redbuds, and other early-blooming plants. Most species are honeybee-sized or smaller; many are dark with distinctive thoracic hair patterns. A square meter of suitable habitat can host hundreds of individual nests of multiple species.

Biology

Mining bees nest underground in vertical burrows. A female:

  1. Selects a patch of bare or sparsely-vegetated soil
  2. Excavates a vertical tunnel 4–24 inches deep, with side branches
  3. Provisions each branch chamber with pollen and nectar; lays an egg
  4. Seals each chamber; eventually closes the main tunnel
  5. Dies; eggs hatch, larvae consume provision, pupate, overwinter

Many Andrena species nest aggregatively — dozens to hundreds of females nesting in close proximity in suitable soil patches. Each individual nest is independent (no colony, no queen), but the spatial concentration makes the aggregations conspicuous. Look for small soil mounds with a central hole on bare patches in spring.

Floral specialization

Many mining bees are oligolectic — specialists on a small set of related plants. Specialists on:

  • Willows — Andrena erythronii, A. salicifloris, others
  • Fruit trees — A. crataegi (hawthorn, apple, cherry)
  • Blueberries — multiple Andrena species
  • Redbuds — A. cercidis
  • [[trout-lily|Trout lily]] — A. erythronii
  • Spring beauty — A. erigeniae

Generalist Andrena species also exist; many are early-spring fliers visiting whatever’s blooming.

Why they matter

  • Early-spring pollination — when [[honeybee|honeybee]] colonies are still building strength after winter, mining bees are doing the bulk of pollination
  • Specialist relationships — many native plant species depend on specific Andrena specialists
  • Resilience — solitary, dispersed populations are less vulnerable to colony collapse

How to host mining bees

  • Leave bare ground patches — many small areas of unmulched, sparsely-vegetated soil
  • Plant early-spring flowering natives — willows, redbuds, serviceberry, native fruit trees, [[trout-lily|trout lily]], spring beauty
  • Avoid disturbing soil — tilling and heavy mulching destroys nest aggregations
  • Tolerate small soil mounds in spring — they are mining bee evidence; they’re harmless and disappear after emergence

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

  • Subset of: [[native-bees]] · [[pollinator]]
  • Member of: [[animal]]

Sources

  • The Bees in Your Backyard, Wilson and Carril
  • USGS Bee Inventory and Monitoring Lab publications
  • Xerces Society pollinator habitat materials

Rooted in life.

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