Willow sand bee
Andrena vaga
The willow sand bee is one of the most prominent solitary wild bee species of early spring. It is characterized by dense, grayish-white hair on the thorax and a shiny black abdomen. The species prefers to nest in self-dug burrows in sandy or loose soils, often forming large aggregations. It is strictly oligolectic, collecting pollen exclusively from willow trees (Salix species).
Details
Identification
Light gray hair on the thorax, shiny black abdomen, black terminal fringe in females.
Social behavior
Solitary, but often forms large nesting aggregations (colonies) with hundreds of nests.
Diet
Strictly specialized on pollen from willow trees (Salix species).
Spawning substrate
Open, sandy, or sparsely vegetated ground patches.
Overwintering
Overwinters as a fully developed adult (imago) within the underground nest cell.
Ecology
Ecological role
Important pollinator of willow plants in early spring.
Natural predators
Cuckoo bees (e.g., Nomada lathburiana), oil beetles, birds, and spiders.
Competitor species
Other willow-specialized sand bees such as Andrena mitis or Andrena nycthemera.
Ecosystem service
Pollination of wild and cultivated willow trees.
Threats
Loss of sandy habitats, river engineering, and removal of willow shrubs.
Scientific profile
Profile
Distinguishing features
Large mining bee (13-15 mm). The thorax is uniformly white-grey haired without a black transverse band (distinction from A. cineraria). The species is strictly oligolectic on Salix. Males have conspicuously long, saber-shaped mandibles and a light-haired face.
Habitat
Floodplains, sand pits, forest edges, inland dunes, parks, and gardens with the presence of willows.
Protection & threats
Main threats
Loss of willow shrubbery due to river engineering; sealing of nesting sites; intensive mowing of dikes; pesticide use in agriculture.
Population trend
Stable; currently classified as least concern in Germany (Red List 2011/2024), regionally benefiting from river restoration projects.
Conservation measures
Preservation and promotion of native willow species; protection of open sandy areas and riparian zones; avoidance of soil sealing in known colony areas.