Nests
Native bees are entirely dependent upon the natural environment for providing viable nesting opportunities. Native bees nest in a variety of places belowground or aboveground; the majority of bee species nest belowground. Belowground nests can be quite simple in architecture, containing a few brood cells to ones that are complex and deep, containing many brood cells. The architecture of aboveground nests is often determined by the nesting substrate and shape of the preexisting cavity. The preexisting cavities are typically formed by wood-boring beetles or other insects that create a sufficiently long linear or meandering cavity that can house multiple brood cells. The female bee preparing the nest carefully waterproofs or lines each brood cell with a glandular secretion, floral oil, or a natural material, then stocks each cell with enough pollen and nectar provisions collected from flowers to feed one developing larva.
Nest Site Selection
For some native bees such as Bombus (bumble bees), selecting a nesting site can be a Goldilocks-like process where the search for and investigation of a potential nest site can last several days to over a week. A female establishing a nest, whether it's a solitary nest or an annual eusocial colony, ultimately selects a site that limits any potential harm to the nest.
A number of factors may influence where a bee chooses to establish a nest such as:
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soil type, texture, moisture, and hardness,
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proximity to viable habitat
(flowering plants, nesting materials),
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history of disturbance (thick plant debris, bare soil, recently burned),
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presence of insulating materials such as those found in an abandoned rodent nest,
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risk of the nest flooding, drying out, or freezing,
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size and depth of the cavity or nesting substrate,
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presence of natural enemies, and
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competition for sites from other insects.
In early May, a Bombus impatiens (common eastern bumble bee) gyne (female), investigates a possible nesting site under leaf litter. Bumble bees use olfactory sensory to find nest sites, identifying the location of old rodent nests via the unique odors emitted.
Types of Nests
Ground Nests
The majority of bee species, approximately 76%, nest belowground in shallow or extensive burrows excavated by a female. Some ground-nesting female bees reuse the emergence hole from their natal nest as a starting point for their new nest, but many establish a new nesting site nearby.
The soil type often dictates where a particular bee may nest. For example, some bees prefer to nest in sandy areas while others prefer the structure provided by a dense loam or silt-loam soil. When female bees excavate soil from their nest, many species pile the excavated soil around the opening of the nest entrance forming a tumulus. Ground-nesting bee nests often resemble ant hills but have one burrow entrance and a well-formed tumulus.
Cavity Nests
For the remaining bees (24%) that nest aboveground, most seek preexisting cavities (holes) in wood (standing dead trees, fallen logs on the ground) or cavities in the stems of soft woody branches and herbaceous flower stalks. Osmia simillina, a mason bee, has been found nesting in snail shells. A minority of cavity-nesting bees excavate their own cavity in wood, pithy flower stalks, or the branches of soft pithy wood such as Sambucus (elderberry) or Rhus (sumac). Some bee species in the genus Dianthidium construct free-form nests attached to a twig or branch that consist of pebbles and resin.
An Augochlora pura (pure green metallic sweat bee) female guards her nest entrance in a log lying on the ground.
Nest Size and Architecture
Ground Nests
The architecture of ground nests can vary considerably among different bee genera and even bee species. Some bees have shallow burrows (5" deep) with a few lateral tunnels while others have extensive and deep branching nests (24-30" deep). Compared with solitary bees that provision nests for approximately three to four weeks, some social ground-nesting bees in the family Halictidae may have active and extensive nests producing multiple generations over the entire growing season.
Females first excavate a main burrow, then often begin excavating the first brood cell at the deepest point or bottom of the burrow. When a brood cell is fully provisioned, females move soil from the excavation of the next brood cell above to backfill the completed one below. Excess soil is pushed to the surface and either accumulates around the nest entrance forming a soil mound called a tumulus or, using their legs, females sweep the soil away from nest entrance. Females use their pygidial plate (a flattened area on the end of their abdomen) as a tamping tool to shape the walls of the tunnels and the brood cells. Once the soil walls are smooth from tamping, females apply a waterproofing material, usually a bodily fluid secreted from their Dufour's gland, a gland located in the end of their abdomen.
When the offspring in the nest complete their metamorphosis and emerge as adults, they dig their way out of the ground vertically, creating many emergence holes clustered around where their mother excavated the original burrow entrance the prior year.
Waterproofing
In belowground nests, the risk of the soil becoming saturated with water is high. Bees have a number of methods and strategies to limit moisture from penetrating the brood cell, preventing the provisions from spoiling and minimizing the growth of mold. Most bees use an oily or waxy secretion produced from their Dufour's gland, a gland positioned at the end of their abdomen. Colletes (cellophane bees) combine secretions from the Dufour's gland with their saliva as they brush the materials on the brood cell walls with their short bilobed (two-lobed) glossa. This lining, after drying, is cellophane-like, forming a waterproof sac to hold the liquid provisions. Macropis (loosestrife oil-collecting bees) collect, then apply floral oil to the walls of their brood cells.
Cavity Nests
In general, soft woody branches or plant stems provide linear aboveground cavities whereas, the architecture of nests in decaying wood may include enlarged rounded chambers or meandering or non-linear cavities formed by beetle larvae borings.
For bee species that use preexisting cavities, the cavity diameter (and the physical size of the bee) serves as a predictor of what type of bee chooses that cavity as a nest: Small bees such as Heriades (small resin bees) nest in cavities with an average diameter of 3.2 mm (1/8 in), whereas a medium-sized bee such as Megachile may use a diameter of 9.5 mm (3/8 in).
A cluster of solitary Colletes inaequalis nests. Some bee species form nesting aggregations, composed of several to hundreds of solitary nests occupying one site.
A social Halictus ligatus nest. Social, semi-social, and communal nests have nest guards that block entry of cuckoo bees and other nest predators or parasites.
An Augochlora pura female excavates a nest in a decaying log lying on the ground.
Nesting Materials
Other than cleptoparasitic (cuckoo) bees in the family Megachilidae, all of the nesting bees in this family use natural materials to line and partition their brood cells. In addition, stem-nesting bees in the genus Ceratina (family Apidae) reuse pith excavated from plant stems to line and partition their brood cells. Collectively, approximately thirteen percent of bee species in Minnesota rely on the availability of natural materials within their habitat and flight range to line and partition their nests. Many of the materials used have antimicrobrial properties and help waterproof the brood cell. The natural materials that bees incorporate into their nests include mud, pith, pebbles, plant hairs, wood fiber or fragments, plant resin, flower petals, and plant leaves.
Leaf Pieces
Bees in the genus Megachile line, partition, and cap their nests with leaf pieces. Bees in this genus are referred to as leafcutter bees, an apt description of this behavior. A Megachile female lands on the edge a chosen plant, clips a small amount of leaf tissue with her mandibles, then moves up or down the leaf edge from this initial cut. Using her large mandibles that have numerous sharp teeth, she cuts the leaf tissue in a scissor-like fashion, turning her body to cut either a circular- or oval-shaped piece. Overlapping pieces of the oval-shaped leaves are used to line each brood cell in the cavity or belowground nest. Multiple circular-shaped leaves form the cap on the end of the nest cavity. Using DNA barcoding, MacIvor (2016) identified the plant species for fifty-four plants. The majority of the plant leaves analyzed (forty-eight) had antimicrobrial properties. The author also theorized that besides antimicrobrial properties, Megachile may select leaves based upon leaf properties such as thickness, texture, or presence or absence of hairs.
A Megachile nest plug of leaf pieces.
A Megachile female arranges cut leaf pieces in her cavity nest.
Three Megachile brood cells wrapped in oval-shaped leaf pieces.
Plants Sourced for Leaf Pieces
Scientific Name | Common Name |
|---|---|
Acer ginnala | Amur maple * invasive * |
Acer platanoides | Norway maple * invasive * |
Acer rubrum | red maple |
Acer saccharinum | silver maple |
Acer saccharum | sugar maple |
Ageratina altissima | white snakeroot |
Amelanchier | serviceberry |
Amphicarpaea bracteata | American hog-peanut |
Asimina triloba | common pawpaw |
Betula | birch |
Brunnichia ovata | American Buckwheat Vine |
Celastrus | bittersweet vine |
Cercis canadensis | eastern redbud |
Chamaenerion angustifolium | fireweed |
Circaea canadensis | broadleaf enchanter's nightshade |
Cornus alternifolia | pagoda dogwood |
Cornus racemosa | gray dogwood |
Cornus sericea | red osier dogwood |
Corylus americana | American hazelnut |
Desmodium spp. | ticktrefoils |
Dioscorea bulbifera | air potato |
Diospyros virginiana | American persimmon |
Dirca palustris | leatherwood |
Erigeron philadelphicus | Philadelphia fleabane |
Fagus grandifolia | American beech |
Fragaria vesca | wild strawberry |
Fragaria virginiana | Virginia strawberry |
Fraxinus americana | white ash |
Fraxinus pennsylvanica | green ash |
Gaylussacia ursina | bear huckleberry |
Hylodesmum glutinosum | pointed-leaved tick-trefoil |
Impatiens capensis | common jewelweed |
Impatiens pallida | pale jewelweed |
Lindera benzoin | northern spicebush |
Liriodendron tulipifera | tulip tree |
Lonicera maackii | Amur honeysuckle |
Magnolia fraseri | Fraser Magnolia |
Oenothera biennis | evening primrose |
Parthenocissus quinquefolia | Virginia creeper |
Passiflora incarnata | purple passionflower |
Passiflora lutea | yellow passionflower |
Persicaria virginiana | American jumpseed |
Phlox paniculata | wild phlox |
Physostegia virginiana | obedient plant |
Platanus occidentalis | American sycamore |
Polemonium reptans | Jacob's ladder |
Populus tremuloides | quaking aspen |
Prunus serotina | black cherry |
Pyrularia pubera | Buffalo-nut |
Quercus rubra | northern red oak |
Rhus glabra | smooth sumac |
Rhus typhina | staghorn sumac |
Rosa blanda | smooth wild rose |
Rubus occidentalis | black raspberry |
Sassafras albidum | sassafras |
Symphoricarpos | wolf berry |
Thalictrum dasycarpum | tall meadowrue |
Tilia cordata | European linden |
Vitis riparia | riverbank grape |
Vitis rotundifolia | muscadine |
Desmodium
Ticktrefoils
Oenothera
Evening Primrose
Parthenocissus
Woodbine/Virginia Creeper
Quercus
Oak
Rosa
Rose
Vitis
Wild Grape
Plant list (Minnesota and eastern United States) exported 2/11/2025 from: Forsberg, B. and Satyshur, C. (admin.). Megachile bee leaf cuts project, iNaturalist. https://www.inaturalist.org/projects/megachile-bee-leaf-cuts
Participatory Science Opportunity
iNaturalist Megachile Bee Leaf Cuts Project
The Minnesota Bee Atlas researchers have created a collection project on iNaturalist to catalog photos of plants used by leafcutter bees. Community scientists are encouraged to join the project and upload their photos of plants with leafcutter bee cuts.
Masticated Leaves
Bees in the genera Ashmeadiella, Hoplitis, Megachile, and Osmia line, partition, and cap their nests with masticated (chewed) leaves. A female cuts the leaf tissue with her mandibles and chews it to form a pesto-like pulpy leaf mixture. Once a ball of masticated leaf tissue is produced, she flies it back to her nest, clasping it in her mandibles. A comprehensive plant list of plants sourced for masticated leaves is not yet available, but observations in central Minnesota indicate that plants in the family Rosaceae may be preferentially used by some Osmia. These include Fragaria (strawberry), and Potentilla and Drymocallis (cinquefoils).
An Osmia female collecting
Fragaria leaf tissue.
A Fragaria virginiana (wild strawberry) leaf with Osmia chew marks.
An Osmia nest plug of masticated leaves.
Masticated leaf partitions inside an Osmia pumila nest, likely sourced from nearby Fragaria virginiana (wild strawberry).
Plants Sourced for Leaf Tissue
Drymocallis arguta (tall cinquefoil)
Fragaria spp. (wild strawberry)
Potentilla (cinquefoil)
Plant Resin
Bees in the genera Dianthidium, Heriades, Megachile, and Paranthidium collect resin from plants to line, partition, and seal their nests or to bind together pebbles or sand particles. Like most of the leaves and hairs collected as nesting materials, resin has antimicrobrial properties that help protect the developing larva in a brood cell. Resin is also waterproof and helps regulate nest moisture, maintaining optimal conditions inside the nest to keep the larva healthy and limit spoilage of the provisions.
From an analysis of the resins used by stem-nesting bees in the Minnesota Bee Atlas project, Colleen Satyshur and colleagues determined that Megachile campanula and Heriades carinata collect resin from conifer trees (likely pine and/or spruce) as well as Populus. Learn more about this project and results here. In Europe, Drescher et al. (2019) analyzed resins in Apis mellifera (honey bee) colonies and determined the resins were sourced from Populus tree buds (balsam poplar), Betula (birch), and Aesculus (buckeye). Similarly, these resins have antimicrobrial properties and likely help keep the colony healthy.
Pine resin flowing on Pinus resinosa (red pine) bark.
Resin bead on a Populus deltoides (eastern cottonwood) bud.
Paranthidium jugatorium, a ground-nesting bee, lines and partiitons each consecutive nest cell with plant resin (gum). Evans (1993) hypothesized that females collected resins or gums from one or more of their pollen host plants including Grindelia and Heterotheca, both found in the same sandy habitat as the nests.
Dianthidium simile nests in sandy prairies, establishing nests in the ground at the base of bunch grasses. This solitary bee uses conifer resin to bind sand particles and pebbles together to form clusters of brood cells.
Another benefit of resin use proposed by Chui et al. (2022) is the volatile organic compounds (VOCs) produced by the resins may help mask the smell of the nest, helping to prevent its discovery by cuckoo bees and other natural enemies.
A cavity nest sealed with resin.
Resin partitions in a stem nest.
A Heriades female removes resin from an old nest.
Plant Hairs
Bees in the genera Anthidium and Pseudoanthidium card or collect plant hairs (trichomes) to line and partition brood cells. These bees are commonly called carder or wool carder bees. Females have large mandibles with numerous teeth that scrape and collect plant hairs as they move across a leaf, plant stem, or flower bud. Once a sizeable ball of hairs is collected under the female, she flies back to her nest, clasping the mass of hairs in her mandibles.
Graham et al. (2017) examined the volatile organic compounds (VOCs) released from plants after carding damage and noted that there was an increase in visitation to the damaged plant by Anthidium females. They theorized that the bees were using the VOCs as cues to assist them in finding plants with hair resources.
Carded hairs and cocoons from an old Anthidium nest.
A non-native Anthidium oblongatum female cards plant hairs from an Artemisia ludoviciana plant to use as a nest lining.
Mud
In Minnesota, one species in the genus Chelostoma (Chelostoma philadelphi) and two bee species in the genus Osmia—Osmia lignaria and O. simillina—are known to use mud to partition and line their nests. Osmia lignaria nests in preexisting cavities in holes in wood, stems, and occasionally in abandoned wasp nests. Osmia simillina is known to nest in snail shells. These mason bees seek out moistened soil of the right texture and consistency. Once found, they land on the ground, then gather up a bolus of moist soil with their mandibles. Females make multiple trips back and forth to the mud source, applying layer after layer to line and partition each brood cell. Once dry, the hardened material helps regulate moisture in the cell and deters access to natural enemies.
An Osmia lignaria female applies a layer of mud inside her cavity nest.
Nest Substrate and Partition Material
Scientific Name | Nest Substrate/Location | Nest Partitions and Plug |
|---|---|---|
Anthidiellum boreale | free-form nests | pebble and resin nests attached to vegetation |
Anthidium manicatum | cavities | carded plant hairs |
Anthidium oblongatum | cavities | carded plant hairs |
Anthidium psoraleae | ||
Anthidium tenuiflorae | ground | carded plant hairs and pebbles |
Anthophora terminalis | wood | sawdust, wood fibers |
Ashmeadiella bucconis | stems (Krombein 1967) | masticated leaves |
Augochlora pura | wood | wood fibers |
Ceratina calcarata | plant stems, holes in wood | pith |
Ceratina dupla | plant stems, holes in wood | pith |
Ceratina mikmaqi | plant stems, holes in wood | pith |
Ceratina strenua | plant stems, holes in wood | pith |
Chelostoma philadelphi | wood | mud partitions, mud and pebble closure |
Dianthidium parvum | exterior surfaces | |
Dianthidium pudicum | exterior surfaces, under rocks | pebbles, resin, other plant debris |
Dianthidium simile | ground in sand | resin from conifers (O'Brien 2007), sand grains and plant debris |
Heriades carinata | stems | resin |
Heriades leavitti | stems | resin |
Heriades variolosa | stems | resin |
Hoplitis albifrons | stems | masticated leaves mixed with pebbles, just pebbles |
Hoplitis pilosifrons | stems | masticated leaves mixed with pith |
Hoplitis producta | elder, sumac or rose stems | masticated leaves |
Hoplitis spoliata | dead sumac stems | masticated leaves |
Hoplitis truncata | stems | |
Hylaeus affinis | plant stems | saliva and Dufour’s gland secretion |
Hylaeus annulatus | plant stems | saliva and Dufour’s gland secretion |
Hylaeus basalis | plant stems | saliva and Dufour’s gland secretion |
Hylaeus fedorica | plant stems | saliva and Dufour’s gland secretion |
Hylaeus floridanus | plant stems | saliva and Dufour’s gland secretion |
Hylaeus illinoisensis | plant stems | saliva and Dufour’s gland secretion |
Hylaeus leptocephalus | plant stems | saliva and Dufour’s gland secretion |
Hylaeus mesillae | plant stems | saliva and Dufour’s gland secretion |
Hylaeus modestus | plant stems | saliva and Dufour’s gland secretion |
Hylaeus nelumbonis | plant stems | saliva and Dufour’s gland secretion |
Hylaeus rudbeckiae | plant stems | saliva and Dufour’s gland secretion |
Hylaeus saniculae | plant stems | saliva and Dufour’s gland secretion |
Hylaeus sparsus | plant stems | saliva and Dufour’s gland secretion |
Hylaeus verticalis | plant stems | saliva and Dufour’s gland secretion |
Lasioglossum cressonii | wood | |
Lasioglossum nigroviride | wood | |
Lasioglossum oblongum | wood | |
Lasioglossum subviridatum | wood | wood fibers |
Megachile addenda | ground, sandy soil | leaf pieces |
Megachile brevis | plant stems, preexisting cavities in substrates above or belowground | leaf pieces and petals |
Megachile campanulae | cavities | resin, wood fiber |
Megachile centuncularis | sumac stems, burrows in ground, mud dauber nests | leaf pieces |
Megachile circumcincta | cavities in the ground | |
Megachile dakotensis | cavities in the ground | |
Megachile fortis | cavities in the ground | |
Megachile frigida | cavities | leaf pieces |
Megachile frugalis | cavities | leaf pieces, masticated leaves, soil |
Megachile gemula | cavities | |
Megachile inermis | cavities | leaf pieces, masticated leaves, wood, mud |
Megachile inimica | wood | leaf pieces, masticated leaves, pebbles |
Megachile lapponica | cavities | leaf pieces, plug other material |
Megachile latimanus | cavities in the ground | |
Megachile melanophaea | cavities in the ground | |
Megachile mendica | Rose canes, sumac branches | leaf pieces |
Megachile montivaga | ground, stems, live thistle stems (Orr et al. 2015) | petals |
Megachile parallela | ||
Megachile petulans | ||
Megachile pugnata | cavities | leaf pieces, masticated leaves and mud cap |
Megachile relativa | cavities | leaf pieces, capped with masticated leaves |
Megachile rotundata | cavities | leaf pieces, infrequently petals |
Megachile rugifrons | ||
Megachile texana | cavities in the ground, under rocks | leaf pieces |
Osmia albiventris | wood (Cane 2007) | masticated leaves, pebbles in cap |
Osmia atriventris | bark, stem, wood (Cane 2007) | masticated leaves |
Osmia bucephala | wood (Cane 2007) | wood fiber from nest and masticated leaves |
Osmia caerulescens | wood, plant stems | masticated leaves |
Osmia collinsiae | wood | |
Osmia conjuncta | snail shells (Rau 1937) | |
Osmia cyaneonitens | ||
Osmia distincta | cavities | |
Osmia felti | unknown | |
Osmia georgica | wood (Cane 2007) | masticated leaves |
Osmia inermis | exterior surfaces, clusters under rocks (Cane 2007) | masticated leaves |
Osmia inspergens | exterior surfaces | |
Osmia laticeps | dead wood | |
Osmia lignaria | wood, stems, wasp nest reuse (Cane 2007) | mud |
Osmia nearctica | ||
Osmia nigriventris | wood (old stumps) (Cane 2007) | masticated leaves |
Osmia proxima | wood, stem (Cane 2007) | masticated leaves |
Osmia pumila | wood, stems including Rosa (Cane 2007) | masticated leaves |
Osmia simillima | oak apple galls, wood (Cane 2007) | mud |
Osmia subarctica | ||
Osmia tersula | wood, stems (Cane 2007) | masticated leaves |
Osmia virga | ||
Paranthidium jugatorium | burrows of other insects in the ground | Resin (Evans 1993) from Grindelia squarrosa |
Pseudoanthidium nanum | cavities | plant hairs |
Minnesota Department of Natural Resources, Minnesota Bee Species List (August 2023). https://files.dnr.state.mn.us/eco/mcbs/mn-statewide-bee-list.pdf
Participatory Science Opportunity
University of Minnesota Extension - Minnesota Native Bee Atlas
The Minnesota Bee Atlas is a research project that relies on volunteers to learn more about the distribution and diversity of Minnesota's 500+ bee species. Some projects are complete but project coordinators and researchers are still seeking volunteers to help with ongoing projects.
The stem-nesting bee monitoring project that started in 2016, wrapped up in June 2024. View the results of this project and the occupants found in the stem nests.
Explore Bee Families
Citations and Further Reading
Cane, J. H., Eickwort, G. C., Wesley, F. R., & Spielholz, J. (1983). Foraging, grooming and mate-seeking behaviors of Macropis nuda (Hymenoptera, Melittidae) and use of Lysimachia ciliata (Primulaceae) oils in larval provisions and cell linings. American Midland Naturalist, 257-264.
Cane, J. H., Griswold, T., & Parker, F. D. (2007). Substrates and materials used for nesting by North American Osmia bees (Hymenoptera: Apiformes: Megachilidae). Annals of the Entomological Society of America, 100(3), 350-358.
Lau, P., Lesne, P., Grebenok, R. J., Rangel, J., & Behmer, S. T. (2022). Assessing pollen nutrient content: a unifying approach for the study of bee nutritional ecology. Philosophical Transactions of the Royal Society B, 377(1853), 20210510.
MacIvor, J. S. (2016). DNA barcoding to identify leaf preference of leafcutting bees. Royal Society Open Science, 3(3), 150623.
Portman, Z. M., Gardner, J., Lane, I. G., Gerjets, N., Petersen, J. D., Ascher, J. S., ... & Cariveau, D. P. (2023). A checklist of the bees (Hymenoptera: Apoidea) of Minnesota. Zootaxa, 5304(1), 1-95.
Vaudo, A. D., Patch, H. M., Mortensen, D. A., Tooker, J. F., & Grozinger, C. M. (2016). Macronutrient ratios in pollen shape bumble bee (Bombus impatiens) foraging strategies and floral preferences. Proceedings of the National Academy of Sciences, 113(28), E4035-E4042.