Roughly three-quarters of all wild bee species nest in the ground, spending much of their life cycle underground in self-excavated burrows.{1Ecological Entomology. Nesting habitat of ground‐nesting bees: a review} When most people picture bees, they imagine a wax-comb hive dangling from a tree branch or tucked inside a beekeeper’s box. That image represents a tiny fraction of bee diversity. The vast majority of the world’s roughly 20,000 bee species are solitary, and most of those dig their own tunnels in soil, raise their offspring in sealed underground chambers, and never produce a drop of harvestable honey. These “underground bees” are everywhere, from backyard lawns and farm fields to desert flats and tropical forests, and their hidden lives are far more elaborate than a simple hole in the dirt would suggest.
Which Bees Live Underground
The ground-nesting habit is spread across many bee families, not confined to one lineage. Mining bees in the genus Andrena are among the most familiar in temperate regions, often appearing in spring lawns as small mounds of excavated soil. Sweat bees (Halictidae) are another enormous group, with thousands of species worldwide that tunnel into bare earth. Cellophane bees (Colletes) get their common name from the plastic-like lining they apply to their underground cells. Long-horned bees, squash bees (Peponapis), and many others round out the list. Even some stingless bees in tropical regions nest below the surface rather than in tree cavities.{2International Journal of Tropical Insect Science. Indigenous knowledge of ground-nesting stingless bees in southwestern Ethiopia} The majority of bee species worldwide are solitary and nest in soil or earthen substrate.{3PubMed. Solitary Ground-Nesting Bees: Opportunities and Challenges for Crop Pollination Management}
This habit is ancient. Fossil bee nests from the Late Cretaceous of Patagonia, composed of inclined tunnels with cells attached by short necks, match the architecture of modern halictine bees. They represent some of the oldest evidence of bees in the entire fossil record and the first such find from the Southern Hemisphere.{4Palaeogeography, Palaeoclimatology, Palaeoecology. Fossil bee nests, coleopteran pupal chambers and tuffaceous paleosols from the Late Cretaceous Laguna Palacios Formation, Central Patagonia (Argentina)} Ground-nesting, in other words, is not some quirky side strategy. It is likely close to the ancestral condition for bees as a group.
What the Nests Look Like
A typical ground-nesting bee nest begins with a single entrance hole, often just a few millimeters across, sometimes surrounded by a small mound of excavated soil called a tumulus. Below the surface, the female digs a main shaft that descends vertically or at an angle, sometimes reaching 30 centimeters or more. Off this main tunnel, she excavates individual brood cells, each one a small oval chamber slightly larger than the bee herself. She provisions each cell with a lump of pollen mixed with nectar, lays a single egg on top, then seals the cell shut with a plug of soil. One female may construct a handful of cells over her short adult life, then die before her offspring emerge.
Not all species follow exactly this blueprint. Some build branching tunnel systems. Others dig shallow, nearly horizontal burrows. But the basic pattern of a tunnel leading to individually sealed, provisioned cells is remarkably consistent across unrelated lineages.
Soil Preferences Are Surprisingly Specific
You might assume any patch of dirt would work, but ground-nesting bees are picky about where they set up shop. Research in commercial fruit orchards found that soil stoniness and soil temperature were positively correlated with bee abundance, while vegetation cover, soil moisture, and hydraulic conductivity were negatively correlated with their numbers.{5CentAUR (University of Reading). Nesting preferences of ground-nesting bees in commercial fruit orchards} In plain terms, they like warm, somewhat stony, well-drained ground with sparse plant cover. Habitats with more bare ground consistently support more ground-nesting bees.{6Global Ecology and Conservation. Ground-nesting bees prefer bare ground areas on calcareous grasslands}
Studies of the gregarious bee Dieunomia triangulifera confirm and expand this picture. Females preferred moist, compact soil with an irregular surface, nested near visual landmarks, avoided heavily vegetated spots, and favored areas with warmer surface temperatures and brighter light. Although it might seem like ground-nesting bees should never run short of nesting sites, relatively little of any given landscape meets all of their criteria at once, which may help explain why many species cluster their nests into dense aggregations.{7Ecological Entomology. Nest site preference and success in a gregarious, ground‐nesting bee Dieunomia triangulifera}
Despite how common ground-nesting is, researchers have noted that quantitative data on nesting habitat requirements remain thin. We know far more about what flowers bees visit than about the soil conditions their offspring need to survive.{8Ecological Entomology. Nesting habitat of ground‐nesting bees: a review}
Waterproofing With Homemade Plastic
One of the more remarkable aspects of underground bee biology is how females protect their brood cells from water and fungi. Many species line their cells with secretions from a structure called the Dufour’s gland. In bees of the genus Colletes, the lining is extraordinary: a transparent, waterproof membrane made of a natural polyester. The bee secretes precursor chemicals, mainly long-chain hydroxy fatty acids stored as lactones in her gland, and a condensation reaction on the cell wall produces a tough polymer.{9PubMed. Natural Polyesters: Dufour’s Gland Macrocyclic Lactones Form Brood Cell Laminesters in Colletes Bees} The result resembles cellophane and is chemically similar to synthetic polyester, which is why Colletes species are sometimes called cellophane bees.
Other genera use different chemical strategies. In Andrena and Lasioglossum, analysis of brood cell linings shows that the volatile chemicals in the lining match those found in the female’s Dufour’s gland, confirming that the gland is the source of the coating material.{10PubMed. Dufour’s gland secretion in the cell linings of bees (Hymenoptera: Apoidea)} These coatings serve double duty: they keep moisture from spoiling the pollen provisions and they may inhibit the growth of mold and bacteria in the damp underground environment.
Microbes in the Nursery
The brood cells of underground bees are not sterile. In cellophane bees of the genus Ptiloglossa, the larval food provisions are dominated by lactobacilli, the same group of bacteria used in yogurt and sourdough. These brood cells smell distinctly fermentative, and metagenomic data indicate that the bees culture multiple species and strains of Apilactobacillus that circulate between bees and the flowers they visit. Compared with other bee species, Ptiloglossa provisions contain a much higher ratio of bacterial to plant biomass.{11PubMed Central. Bee breweries: The unusually fermentative, lactobacilli-dominated brood cell microbiomes of cellophane bees}
In solitary alkali bees, the microbiome of feeding larvae closely resembles that of their pollen provisions, with low variation from nest to nest. But once larvae stop feeding and enter the pre-pupal stage, their microbiome shifts to resemble the brood cell walls and newly emerged adult females, suggesting that the bee picks up a different microbial community from the soil itself as it matures.{12Ecological Entomology. Composition and acquisition of the microbiome in solitary, ground-nesting alkali bees} Whether these microbes are beneficial passengers, neutral hitchhikers, or something the bee actively cultivates is still an open question for most species.
Solitary but Sometimes Social
Most ground-nesting bees are solitary in the strict sense: each female builds and provisions her own nest without help. But “solitary” does not always mean “alone.” Many species nest in dense aggregations, with hundreds or thousands of individual nest entrances packed into a small patch of bare ground. Each hole belongs to a single female, but the neighborhood effect can be striking. These aggregations often return to the same site year after year.
The line between solitary and social can blur in interesting ways. Experiments with the normally solitary sweat bee Lasioglossum NDA-1 showed that when two females were forced to share a nest, a division of labor repeatedly emerged: one bee specialized in digging and tamping soil while her nestmate stood guard at the entrance. This specialization could not be explained by one bee simply being more active than the other. Instead, it appeared to be an emergent property of the social interaction itself, hinting at how more complex bee societies might have evolved from solitary ancestors.{13Ethology. Emergence and Consequences of Division of Labor in Associations of Normally Solitary Sweat Bees}
Cuckoo Bees and Underground Warfare
Underground nests are valuable targets for parasites. Cuckoo bees, found across multiple bee families, are brood parasites that sneak into a host bee’s nest and lay their own egg on the stored pollen provisions. The provisions are not enough to feed both the host’s larva and the parasite’s, so the parasite larva kills the host offspring to claim the food for itself. This creates intense evolutionary pressure: host bees have developed behaviors to detect and repel intruders, while cuckoo bees have evolved to avoid detection.{14PubMed Central. Under the radar: detection avoidance in brood parasitic bees}
Some cuckoo bees have lost the ability to collect pollen entirely. They lack the specialized hairs (called scopae) that other bees use to carry pollen, because they never need to provision a cell themselves. Their entire reproductive strategy depends on exploiting the underground labor of their hosts. This is one reason dense nesting aggregations can be a double-edged sword: more neighbors may offer some safety in numbers, but a large aggregation also presents a rich target for parasites.
Underground Engineers of the Soil
Pollination gets most of the attention, and rightly so, since the vast majority of flowering plants depend on animal pollinators.{15PubMed Central. Regard and protect ground-nesting pollinators as part of soil biodiversity} But ground-nesting bees also reshape the soil itself in ways that are only beginning to be studied. Their tunnels create macropores, vertical channels that connect the surface to deeper layers. These channels function much like the burrows of earthworms, enhancing water infiltration and allowing air to penetrate deeper into the ground. At high nesting densities, sometimes exceeding 50 nest holes per square meter, the cumulative effect on water and gas transport is likely significant, although it has not yet been precisely quantified.{16Basic and Applied Ecology. Beyond pollination – The neglected contribution of ground-nesting bees to soil functions}
The excavated soil brought to the surface also mixes layers in a process analogous to bioturbation by earthworms. And the organic material left behind in abandoned cells, leftover pollen, dead larvae, shed pupal skins, adds nutrients to the soil profile. Researchers have begun arguing that ground-nesting bees deserve attention not only as pollinators but as part of the soil biodiversity that keeps agricultural and natural ecosystems functioning.
Tillage, Pesticides, and Other Threats
Because their nests are in the ground, these bees face a threat that cavity- and twig-nesting bees do not: the plow. A review of studies on tillage impacts found that tilled fields showed either no effect or a negative effect on ground-nesting bee populations compared with no-till systems. Tillage can physically crush bees and their brood, destroy the tunnel architecture, displace brood cells, and change the soil moisture and temperature conditions that developing larvae need.{17Agriculture, Ecosystems & Environment. A review of soil tillage impacts on ground-nesting wild bees – mechanisms, implications, and future research perspectives} Research on the squash bee Peponapis pruinosa in California found that tillage reduced offspring emergence by roughly half compared with no-till plots.{18Agriculture, Ecosystems & Environment. Impact of tillage on the crop pollinating, ground-nesting bee, Peponapis pruinosa in California}
Pesticides add a second layer of risk. Because ground-nesting bees literally live inside treated soil, they face exposure routes that honeybees in above-ground hives do not. Risk assessments for neonicotinoid insecticides in agricultural soil found that under chronic exposure scenarios, the probability of exceeding lethal doses for a solitary bee surrogate was alarmingly high for certain compounds, with clothianidin in crop fields exceeding lethal thresholds for solitary bees in over two-thirds of modeled scenarios for cucurbit crops.{19Scientific Reports. Assessment of risk to hoary squash bees (Peponapis pruinosa) and other ground-nesting bees from systemic insecticides in agricultural soil}
The picture is not uniformly grim, though. A study that allowed the hairy-footed flower bee (Anthophora plumipes) to nest freely in loam blocks dosed with imidacloprid found that measured residues in brood provisions and bee bodies remained below a hundredth of a percent of the soil concentration, suggesting limited migration of the chemical from soil into the brood. At the concentrations tested, there was no marked effect on offspring number, survival, body size, or parasitism rates.{20Apidologie. The ground-nesting bee Anthophora plumipes as a model species for assessing effects of soil-mediated pesticide exposure} How much protection the bees’ cell linings provide against soil contaminants is an active area of investigation, and results likely vary by species and soil type.
Finding the Invisible Majority
One practical challenge in conserving ground-nesting bees is simply knowing where they are. A nest entrance is a hole the diameter of a pencil, surrounded by a small dirt mound that can easily be mistaken for an earthworm cast or an ant hill. Surveys have traditionally relied on patient human observers walking transects and counting holes, which is slow and hard to scale. Researchers have now demonstrated that drone-based aerial photography combined with deep learning models can reliably detect bee nest tumuli across large areas. In a test on a dense aggregation of Lasioglossum malachurum, the automated system achieved high accuracy in distinguishing bee nests from earthworm casts on bare soil.{21PubMed Central. Automated Detection and Monitoring of Ground-Nesting Bee Nests Using Drone Imagery and Deep Learning} If the approach scales, it could transform how land managers identify and protect nesting habitat.
Identifying Ground-Nesting Bees in Your Yard
If you notice small holes appearing in a bare patch of lawn, a garden path, or a flower bed in spring, you are probably looking at a ground-nesting bee aggregation. The telltale signs are pencil-width holes surrounded by tiny volcano-shaped mounds of fine soil, often in sunny, south-facing areas with sparse vegetation. You may see small bees hovering low over the ground or disappearing into the holes.
These bees are almost universally docile. Solitary females can technically sting but rarely do, because they have no colony or honey stores to defend. Males, which often patrol aggregation sites in search of mates, cannot sting at all. Walking through an active aggregation is about as dangerous as walking through a meadow full of butterflies. The biggest mistake homeowners make is reaching for a pesticide. Ground-nesting bees are valuable pollinators for gardens and nearby crops, and their aggregations typically last only a few weeks in spring. The simplest response is to leave them alone. If you actively want to encourage them, maintaining patches of bare, undisturbed, well-drained soil in sunny spots gives them what they need most.
Honey From Below
While most ground-nesting bees are solitary and do not produce storable honey, some tropical stingless bees that nest underground are an exception. In southwestern Ethiopia, the Sheka community has a long tradition of harvesting honey from ground-nesting stingless bees. Honey collectors locate wild nests by watching worker bee flight paths, attaching a thread to a captured worker and following it home, or even listening for the humming sound of wasps that prey on the bees. The knowledge passes between generations, with collectors ranging widely in age and experience.{22International Journal of Tropical Insect Science. Indigenous knowledge of ground-nesting stingless bees in southwestern Ethiopia} Wild nests are harvested destructively, though at least one farmer has kept colonies in purpose-built wooden hives at his homestead.
In the Amhara Region of northwest Ethiopia, a similar tradition exists around ground-nesting Meliponula bees. Local communities use the stingless bee honey, known locally as tazima or tazma mar, both as food and as a treatment in traditional medicine for a range of conditions including pain relief.{23Israel Journal of Entomology. Stingless bee Meliponula Cockerell (Hymenoptera: Apidae: Meliponini) ground nest architecture and traditional knowledge on the use of honey in the Amhara Region, Northwest Ethiopia} These practices highlight that the relationship between humans and underground bees is not limited to temperate gardeners puzzling over lawn holes. In parts of the tropics, it is an old, culturally rich, and economically meaningful connection, and one increasingly threatened by agricultural expansion into the landscapes where these bees nest.