Andrena

Best distinguished from other Andrenidae by the subgenal coronet, a ring of hairs on the underside of the face. Facial foveae are present but also occur in some other Andrenidae genera. The combination of ground-nesting behavior, solitary lifestyle, and morphological features distinguishes Andrena from superficially similar genera in other bee families. Species-level identification requires examination of subtle morphological characters including genitalia, wing venation, and hair patterns.

Medium-sized bees ranging 8–17 mm in body length, with males typically smaller and more slender than females. Most species are black with white to tan hair, though some exhibit reddish, metallic blue, or green coloration. Wings possess two or three submarginal cells. Females carry pollen primarily on femoral scopal hairs, with many species additionally possessing a propodeal corbicula on the thorax. Distinctive velvety facial foveae are present between the compound eyes and antennal bases. A unique identifying feature is the subgenal coronet, a ring of hairs on the underside of the face.

Ground-nesting in various soil types, with documented preference for sandy soils. Nests constructed in bare or sparsely vegetated ground including riverbanks, path-side cuttings, grasslands, and open areas within forests. Some species associated with specific geological substrates such as chalk grassland or heathland. Forest-associated species occupy woodland habitats with spring-blooming flora. Many species require warm, dry, bare soil conditions for successful nest establishment and larval development.

Nearly worldwide distribution absent from Oceania, South America, Australia, and Madagascar. Most diverse in temperate regions of Europe, Asia, and North America, particularly areas with Mediterranean climate. Present in sub-Saharan Africa with limited species representation. In North America, common across temperate and boreal regions. In Europe, widespread with highest diversity in southern regions. Some species exhibit restricted ranges, such as Andrena ghisbaini endemic to southern Spain.

Adults typically active for a few weeks, with most species having one generation per year. Spring-flying species emerge from March to June in temperate regions. Some species active into summer, with flight periods extending from late June through August. Emergence timing varies by latitude and elevation. Males generally emerge before females.

Females collect pollen and nectar to provision brood cells. Many species are oligolectic (host-plant specialists), visiting flowers of only a single plant species or closely related plants. Oligolecty is considered the ancestral condition for the genus. Specialist associations include subgenus Callandrena on Asteraceae pollen, with corresponding morphological adaptations such as highly branched, fluffy scopal hairs. Generalist feeding has evolved multiple times independently across the genus.

Solitary ground-nesting; each female constructs her own nest. After mating, females excavate burrows with multiple cells lined with shiny secretion. Each cell is provisioned with nectar and pollen formed into firm, round pollen masses. One egg is laid per cell. Larvae feed on provisions, do not spin cocoons, and overwinter as adults in the natal cell. Adults emerge the following spring. Some species exhibit communal nesting where females share nest entrances but provision cells independently. Nest aggregations common, with multiple females nesting in proximity.

Females excavate soil burrows creating small tumuli around nest entrances. Males emerge first and patrol nesting areas seeking females; mating often involves multiple males pursuing emerging females. Some species exhibit communal nesting with shared entrances. Adults are short-tongued bees. Stylopization (parasitism by Strepsiptera) can alter host emergence timing and external morphology. Nests are vulnerable to brood parasitism by cuckoo bees (Nomada), blister beetles, parasitic flies, and Strepsiptera.

Important pollinators of spring-blooming wildflowers and trees in forest and open habitats. Oligolectic species provide specialized pollination services to their host plants. Ground-nesting activity contributes to soil aeration and nutrient cycling. Serve as hosts for various parasitic insects including Strepsiptera, maintaining complex food web relationships. Some species may pollinate economically important timber trees including maples, though this requires further documentation.

Important native pollinators in agricultural and natural landscapes. Subject to conservation concern due to habitat loss, particularly loss of bare ground nesting sites and fragmentation of flower-rich grasslands. Some species are rare and localized, receiving targeted conservation efforts such as bare ground creation for Andrena tarsata in the UK. Used as indicator species for habitat quality in heathland and grassland ecosystems. Genome sequencing of Andrena scotica contributes to understanding of bee biology and parasitism.

• Other Andrenidae genera (e.g., Panurginus, Perdita)Also have facial foveae; distinguished by absence of subgenal coronet and different wing venation or body proportions
• Halictidae (sweat bees)Similar size and ground-nesting habits; distinguished by lack of facial foveae, different wing venation, and often metallic coloration
• Colletidae (plasterer bees)Similar solitary ground-nesting behavior; distinguished by smooth, shiny abdomen and cell lining secretions that dry into cellophane-like membranes

• solitary bees
• ground-nesting bees
• mining bees
• pollinators
• oligolectic
• spring bees
• forest bees

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Not-so Solitary Bees - Buglife Blog - Buglife
• Northern Ireland, invertebrate finds in review 2023 - Buglife Blog - Buglife
• In a New Study, Spring Forest Bees Get Their Due
• Bare ground experiments to help save rare bees and wasps - Buglife Blog - Buglife
• What’s in a name….? - Buglife Blog - Buglife
• Bees of the Changing Chalk Partnership Area - Buglife Blog - Buglife
• The nest biology of the bees : Andrena (Melandrena) regularis Malloch and Andrena (Melandrena) carlini Cockerell (Hymenoptera: Andrenidae)
• Andrena Florivaga Eversmann , 1852 (Hymenoptera: Apoidea: Andrenidae) - A New Bee Species of the Genus Andrena in Poland
• The genome sequence of the chocolate mining bee, Andrena scotica Perkins, 1916 (Hymenoptera: Andrenidae).
• Contributions to the Andrena (Hymenoptera, Andrenidae) Fauna of the Mediterranean Region of Türkiye.