Most bees do not live in the familiar wooden box hives that come to mind when you hear the word “bee.” Roughly three-quarters of all bee species nest underground, excavating burrows in bare soil. The rest split among a range of strategies: boring tunnels into wood, occupying hollow plant stems, squatting in abandoned rodent holes, wedging into rock crevices, and, in at least a few species, setting up house inside empty snail shells. Even the managed honeybee, the species most people picture, is a relative oddity in the bee world. Its elaborate wax comb and large perennial colonies represent just one point on a remarkably wide spectrum of bee architecture.
The Majority Are Underground
Ground-nesting is the ancestral and by far the most common nesting strategy across bee families. Species from nearly every major lineage dig their own burrows, typically in patches of bare or sparsely vegetated soil. A female bee selects a site, excavates a tunnel with her mandibles and legs, then shapes small chambers off the main shaft where she provisions each cell with a ball of pollen and nectar before laying an egg on top. She seals the cell, moves on to the next, and usually never sees her offspring emerge.
The range of soil conditions these bees can exploit is enormous. A review of ground-nesting habitat found that species vary widely in their preferences for soil texture, compaction, moisture, temperature, and proximity to flowers or other nesting bees.1Ecological Entomology. Nesting habitat of ground‐nesting bees: a review Some favor loose sandy soils in arid landscapes; others nest in compacted loams along footpaths or clay-rich banks. One study of soil properties at nesting sites found textures ranging from nearly pure sand to silt loams and clay loams, though no bees were found in pure clay or pure silt. Larger-bodied species tended to choose soils with higher clay content, but smaller bees were not confined to shallow depths as you might expect.2Journal of the Kansas Entomological Society. Soils of ground-nesting bees (Hymenoptera: Apoidea): Texture, moisture, cell depth and climate
Many ground-nesters are solitary, meaning each female provisions her own nest independently. But some, like certain sweat bees in the family Halictidae, form loose aggregations where hundreds or thousands of individual nests cluster in the same patch of earth. From a distance these aggregations can look alarming, but each tunnel typically belongs to a single female, and most ground-nesting species are docile and unlikely to sting unless handled.
Cavity Nesters and the Bee Hotel Crowd
A sizable minority of bees skip the digging and instead nest inside pre-existing cavities. Mason bees in the genus Osmia are a classic example: they seek out hollow stems, beetle boreholes in dead wood, gaps in stone walls, and other narrow tubes. The female constructs a linear series of cells inside the cavity, partitioning each one with mud, chewed leaves, or plant resin. Leafcutter bees (Megachile) similarly nest in cavities but line and cap their cells with neatly cut leaf pieces. One North American leafcutter species, for instance, builds cell partitions from a layer of leaf pieces followed by a layer of masticated vegetation and soil particles.3The Great Lakes Entomologist. Minnesota State Records for Osmia georgica, Megachile inimica, and Megachile frugalis (Hymenoptera, Megachilidae), Including a New Nest Description for Megachile frugalis Compared with Other Species in the Subgenus Sayapis
These cavity-nesting habits are the reason “bee hotels” exist. The idea is simple: bundle hollow bamboo tubes or drill holes in a block of wood, hang it in a sunny spot, and cavity-nesting bees will move in. In practice, the results are mixed. A large survey of nearly 600 bee hotels in Toronto over three years found that introduced (non-native) bees occupied about a third of the sites and made up roughly a quarter of all bees and wasps recorded. Native bees suffered higher parasitism rates than introduced bees at the same hotels, and introduced females provisioned nests with more female offspring each year.4PubMed Central. ‘Bee hotels’ as tools for native pollinator conservation: a premature verdict? The concern is that bee hotels, if poorly managed, can become breeding grounds for parasites and disproportionately benefit species that are already common rather than the rare natives they are meant to help.
Carpenter Bees and Life Inside Wood
Carpenter bees take the cavity-nesting concept a step further by creating their own cavities. Rather than finding an existing hole, a female carpenter bee chews directly into dead wood or weathered lumber, excavating a smooth tunnel with her powerful mandibles. The eastern carpenter bee (Xylocopa virginica), common across eastern North America, bores tunnels averaging about 15 centimeters long and 15 millimeters wide, dividing them into cells roughly 18 millimeters each.5PubMed. Eastern Carpenter Bee (Hymenoptera: Apidae): Nest Structure, Nest Cell Provisions, and Trap Nest Acceptance in Rhode Island She provisions each cell with a loaf of pollen and nectar, separates it from the next with a partition of chewed wood pulp, and seals the whole thing off.
Carpenter bees are often blamed for structural damage to decks, pergolas, and eaves, and the piles of sawdust beneath their entrance holes can be striking. But the damage is usually cosmetic unless the same piece of wood is reused by successive generations for many years, which can weaken joists or beams over time. These bees are mostly solitary, though some tropical carpenter bee species show communal or semi-social nesting where multiple females share a single tunnel system.
Bumblebees and Their Borrowed Burrows
Bumblebees are social insects, but they do not build the large perennial colonies that honeybees maintain. A bumblebee queen overwinters alone, emerges in spring, and searches for a suitable nesting site to found a small colony that will last only one season. The classic nesting site is an abandoned rodent burrow, and researchers have confirmed that queens actively seek out rodent scent when selecting nest locations. One study found that synthetic rodent odor lures could guide spring queens to artificial nest boxes, supporting the long-held observation that bumblebees cue on the smell of former rodent occupants.6Insect Conservation and Diversity. Rodent odour bait: A new bumble bee conservation tool to enhance nest box occupancy
Inside the burrow, the queen builds a small wax cup that she fills with honey, then constructs a clump of pollen into which she lays her first batch of eggs. She incubates the brood by sitting on it, vibrating her flight muscles to generate heat. Once the first workers emerge, they take over foraging and brood care. A mature bumblebee colony might have a few dozen to a few hundred workers, a fraction of a honeybee colony’s tens of thousands. Other bumblebee species use grass tussocks, bird boxes, insulation in wall cavities, and even compost heaps. Their flexibility in nesting sites is one reason bumblebees persist in suburban gardens and parks where more specialized ground-nesters struggle.
Honeybees in the Wild
The managed honeybee hive, with its removable frames and stacked boxes, is a human invention. In the wild, honeybee colonies (Apis mellifera) nest inside enclosed cavities, most often tree hollows, but also rock crevices, cliff faces, and occasionally the walls of buildings. A citizen-science survey of wild honeybee colonies in cavities found that most chose sites with small or narrow entrance holes, which help the colony regulate airflow and defend against intruders.7Frontiers in Ecology and the Environment. Cavity occupancy by wild honey bees: need for evidence of ecological impacts
Inside the cavity, honeybees build parallel sheets of beeswax comb hanging vertically from the ceiling. The hexagonal cell layout maximizes storage volume while minimizing wax, with each new cell positioned at the junction of two previously built cells.8PubMed Central. Sub-cell scale features govern the placement of new cells by honeybees during comb construction Imaging analysis of comb has even revealed that bees may deliberately vary the physical density of wax to meet specific structural needs, building denser bridging comb to repair fractures.9PubMed Central. Computational methods for the characterization of Apis mellifera comb architecture
Wild colonies also coat the interior of their cavity with propolis, a mixture of plant resins, wax, and other compounds. This propolis envelope acts as an antimicrobial layer that helps protect brood from bacterial infections. Colonies with a propolis envelope had lower infection levels when challenged with the bacterium that causes American foulbrood, a devastating bee disease, compared with colonies lacking such an envelope.10PubMed Central. Propolis envelope in Apis mellifera colonies supports honey bees against the pathogen, Paenibacillus larvae In managed hives, beekeepers often scrape propolis away as a nuisance, inadvertently weakening this natural defense.
How Bees Control Their Nest Climate
A bee nest is not just a container for larvae; it is a climate-controlled environment. Honeybees are especially sophisticated in this regard. Workers regulate brood-nest temperature by adjusting their density on the comb and their rate of heat production through muscle contractions. When the nest gets too warm, they spread water droplets over comb surfaces and fan their wings to promote evaporative cooling.11PubMed Central. Coping with the cold and fighting the heat: thermal homeostasis of a superorganism, the honeybee colony The goal is to keep brood at roughly 34–36 °C, the narrow range needed for proper larval development.
Wild tree-cavity nests have a natural advantage over man-made hives in maintaining humidity. Modeling suggests that the thicker walls and smaller entrances of natural cavities allow colonies to achieve higher internal humidity more easily and more frequently than the thin-walled wooden boxes used in beekeeping.12PubMed Central. Nectar, humidity, honey bees (Apis mellifera) and varroa in summer: a theoretical thermofluid analysis of the fate of water vapour from honey ripening and its implications on the control of Varroa destructor Humidity matters because it affects honey ripening, wax pliability, and possibly even the survival of parasites like Varroa mites.
Ground-nesting solitary bees face different thermal challenges. They cannot collectively generate heat the way a honeybee colony can, so brood temperature largely depends on soil properties and depth. Many species appear to select nesting sites with favorable sun exposure or soil thermal properties, though individual preferences vary widely among species.
Stingless Bees and Their Resin Fortresses
In the tropics, stingless bees (tribe Meliponini) represent a completely different model of social nesting. These small bees build elaborate nests inside tree hollows, rock crevices, or even termite mounds, and they rely heavily on plant resin rather than wax for construction. Resin serves as both a building material and a chemical weapon: stingless bees use it to construct entrance tubes, walls, and storage pots, and they also deploy it to repel predators and kill nest intruders.13PubMed Central. Resin Use by Stingless Bees: A Review Resin-derived compounds even enrich the chemical profiles on the bees’ bodies and shape the microbial communities living inside their nests.
The link between social behavior and above-ground nesting is not coincidental. A large-scale analysis of over 4,000 bee species found that the evolution of above-ground nesting is closely tied to the evolution of sociality, but this combination has evolved rarely across bee evolutionary history. Where it does arise, species that are both social and above-ground nesters tend to occupy warmer, wetter, less seasonally variable climates, which is why they dominate tropical bee communities.14bioRxiv. Sociality and nesting strategy shape the bimodal diversity gradient in bees
Snail Shells, Cuckoo Bees, and Other Oddities
Some bee nesting strategies sound almost made up. Several Osmia species in Europe nest exclusively inside empty snail shells. The bee finds a shell of the right size, constructs brood cells inside, seals the opening, and sometimes covers the shell with grass or plant material for camouflage. Researchers studying one such species, Osmia conjuncta, found that females prefer shells of intermediate size and color and avoid shells located near shrubs.15The Canadian Entomologist. The native snail shell–nesting bee Osmia conjuncta (Hymenoptera: Megachilidae) exploits a local abundance of exotic Cepaea snails (Stylommatophora: Helicidae), choosing empty shells by size, colour, and microhabitat Multiple Osmia species use snail shells as their sole nesting cavity, and the availability of suitable shells can directly limit their populations.16Biological Conservation. Effects of grazing intensity, habitat area and connectivity on snail-shell nesting bees
Then there are the cuckoo bees, which build no nests at all. Like the bird they are named after, cuckoo bees are brood parasites that sneak into the nests of other bee species to lay their own eggs. The cuckoo bee larva typically kills the host’s egg or outcompetes the host larva for the provisions. One documented case involves the cuckoo bee Mesonychium asteria, whose females were observed flying over nest aggregations, attacking nests, and laying eggs inside the brood cells of their host species Centris xanthomelaena.17Sociobiology. Host records and cleptoparasitic behavior of the cuckoo bee Mesonychium asteria (Smith) (Apidae, Ericrocidini) in nests of Centris xanthomelaena Moure & Castro, (Apidae, Centridini) Cuckoo bees have lost the pollen-collecting structures (like leg baskets) that their nest-building relatives depend on, because they never need to provision their own cells.
Bees in the Pavement
City sidewalks and cobblestone plazas might seem like the last place you would find a bee nest, but ground-nesting bees are surprisingly resourceful urban colonizers. Surveys in Brussels documented wild bees and wasps nesting in the gaps and cracks of urban pavements, using the sandy substrate beneath paving stones the same way they would use a natural patch of bare soil.18Insect Conservation and Diversity. Nest aggregations of wild bees and apoid wasps in urban pavements: A ‘street life’ to be promoted in urban planning A parallel survey across twelve locations in Berlin confirmed the pattern, finding that cobbled pavements can foster a surprising number and variety of soil-dwelling insects, including wild bees.19Urban Ecosystems. Urban pavements as a novel habitat for wild bees and other ground-nesting insects
This has practical implications for urban planning. Fully sealing sidewalks with asphalt or concrete eliminates nesting opportunities, while permeable pavements, cobblestones with sand-filled joints, and unsealed edges along roads can maintain habitat for pollinators without compromising pedestrian infrastructure. The bees nesting in these spaces are typically small, inconspicuous solitary species that pose no sting risk to pedestrians.
Farming, Tillage, and What Threatens Ground Nests
Because so many bee species nest underground, anything that disturbs soil can affect them. Agricultural tillage is the obvious concern. A review of the research identified ten studies that assessed tillage impacts on ground-nesting wild bees, finding either no effect or a negative effect of tilled versus no-till systems. The potential damage includes physical injury to bees and their brood, destruction of burrow architecture, displacement of brood cells, and alteration of the soil moisture and temperature around developing larvae.20Agriculture, Ecosystems & Environment. A review of soil tillage impacts on ground-nesting wild bees – mechanisms, implications, and future research perspectives
The picture is more nuanced than “tilling is bad, no-till is good,” however. A study that directly compared tillage systems in arable fields found that nest density was not significantly different between tilled and no-till plots. Instead, nesting was more strongly associated with distance to the field edge, crop cover, soil texture, and landscape context. Nests tended to increase with soil bulk density and sand content, and various ground-nesting species, including important crop pollinators, used arable fields regardless of tillage system.21Journal of Applied Ecology. Nesting of ground‐nesting bees in arable fields is not associated with tillage system per se, but with distance to field edge, crop cover, soil and landscape context The takeaway is that preserving bare-soil margins at field edges and maintaining diverse surrounding landscapes may matter more for ground-nesting bees than the specific tillage method used in the middle of a crop field.
The Oldest Known Bee Nests
Ground-nesting has been the dominant bee strategy for a long time. The oldest known crown-bee nests, discovered in the Castillo Formation of Patagonia, date to roughly 100 million years ago. These fossilized burrows, assigned to a new trace-fossil species, resemble the nests of modern sweat bees in the tribe Halictini, with sessile cells attached to main tunnels. The discovery pushes back the timing of bee diversification and supports the idea that bees diversified rapidly alongside flowering plants during the late Albian period of the Cretaceous.22PubMed Central. 100 Ma sweat bee nests: Early and rapid co-diversification of crown bees and flowering plants In other words, bees have been digging burrows since before most modern mammal lineages existed. The elaborate hives, resin fortresses, and snail-shell nurseries came later, each an evolutionary improvisation on a theme that started with a simple hole in the ground.