Bee Behaviors
While performing tasks to produce the next generation of bees, bees exhibit a wide variety of behaviors. For example, male bees use a number of tactics to find a mate or strategies to find a place to spend the night. Likewise, females use a variety of strategies and techniques to search for a nesting site, construct or excavate a nest, and interact with and collect floral resources from flowers. See some examples below of common bee behaviors.
Nest Orientation
When female bees (and wasps) are constructing and provisioning nests, they must remember where their nest is located to find it when returning multiple times a day. To find their "home-base", females perform a nest orientation walk and/or flight before departing on their first flight of the day. While facing the nest entrance, these nest orientation behaviors can include: 1) walking side-to-side in front of the nest entrance and/or 2) on the wing, briefly hovering over the nest entrance, then flying side-to-side in ever increasing arcs as they move away from the entrance. While performing these orientation flights, the females are learning surrounding landmarks next to and around the nest. When returning to the nest, the bee (or wasp) may perform a similar orientation flight while approaching the nest entrance.
Mate-Finding Behaviors
Male bees have a limited role in a bee's life cycle; they do not help females with preparing or provisioning nests, nor assist with rearing offspring. In some rare cases, they may help with nest guarding. Males are short-lived, with only a brief period of time to find a mate and pass on their genes. To this effort, they allocate a significant amount of time, energy, and tactics. For solitary bees, females usually mate with only one male, leaving many males without an opportunity. To successfully find a mate, males employ a number methods. See below for some of the strategies employed by males to find a mate.
A Colletes inaequalis female and male mate near the ground in the nesting aggregation emergence site.
Patrolling
Patrolling is a strategy employed by males to find a mate. Patrolling involves many males flying in circuitous patterns near the ground by the nest emergence site (for species that nest in aggregations or gregariously) or around flowering plants that females may visit. For example, Colletes inaequalis is a solitary species that nests in aggregations and emerges in early spring. The males emerge several days to over a week prior to the females, then patrol the ground above the nesting site or flowering plants in bloom such as red maple or willow, that females are likely to visit.
Colletes and Andrena males patrol a flowering pussy willow.
A Colletes inaequalis male and female mate on the ground in a large nesting aggregation.
Monitoring Host Plants
Many solitary bees do not nest gregariously (in large nesting aggregations). Their solitary nests are scattered across a landscape. For pollen specialist bees, males can reliably find females visiting their pollen host plants, a strategy that helps males refine or reduce the guesswork of locating females. It's not uncommon to see one or a few males monitoring a host plant, waiting for the females to forage on the host plant. Mating on flowers while females forage on a host plant is a common behavior of some pollen specialists.
A Protandrena female and male mate while a female visits a pollen host plant, Rudbeckia subtomentosa.
Scent-Marking Plants With VOCs
When it's less predictable to find a mate, some males scent-mark a given territory then patrol that territory for females. To scent-mark a territory, the male deposits volatile organic compounds (VOCs) produced from salivary glands on vegetation. For example, cleptoparasitic (cuckoo) bees in the genus Nomada scent-mark plants then patrol the area, waiting for females. Tengö and Bergström (1977) analyzed the chemical compounds of Nomada males' salivary gland secretions and those found in the Dufour's gland of their host, Andrena females, and found that the compounds are identical. Secretions from the Dufour's gland are used by Andrena (and other bee) females to line the soil brood cell walls, giving the nest a unique chemical signature. While Nomada mate, the male deposits a chemical compound produced from the salivary glands on the female.The authors hypothesized that this chemical mimicry may help Nomada females, while entering or moving within a nest, evade detection by their Andrena host.
A Nomada female exits an Andrena nest.
Establishing a Territory
Some solitary and social males establish territories, then patrol the territory for females. At the same time, they defend the territory from intruding bees (and other flying organisms). Using their large eyes and sensory apparatus on their antennae, they continuously scan the landscape for opportunities. These territories are often scent-marked with VOCs produced from their salivary glands. Some Bombus (bumble bee) males establish a territory in sites with flower resources a gyne may visit. Selecting a tall plant for a perch, they launch from their perch to investigate any potential females entering or to drive off unwanted competition. In a boomerang-like pattern, they return to their perch after their chase.
A Bombus auricomus male monitors his territory from a tall perch.
A Bombus auricomus male monitors his territory from a tall perch.
Nectar Robbing
Short-tongued bees are challenged by intricately shaped flowers with hard-to-reach nectaries. Some bees (and wasps) have developed a work around, a behavior called nectar robbing. They chew a hole in the flower corolla near the base of the flower where the nectary is located, then insert their tongue into the hole to feed on the flower's nectar. Once created, a number of insects use these nectar robbing holes. A nectar-robbing bee generally does not interact with the flower's reproductive parts, so these visits ultimately do not help pollinate the plant. Nectar robbing may reduce the plant's fitness as the plant expends extra resources toward the production of nectar with no symbiotic exchange by the pollinator, ultimately destabilizing a potential mutualistic relationship.
A Bombus affinis male chews a hole in each flower corolla to provide an entry point close to the nectary to feed on the flower's nectar.
Concentrating Nectar
After imbibing nectar from flowers, many bees regurgitate the nectar, then expose it to the air in their mouthparts. Bees manipulate the nectar in the mouthparts by repeatedly extending and retracting the mouthparts. Portman et al. (2021) determined that this behavior is widespread, noting that 51 genera from 6 families are known to concentrate nectar. This concentrating nectar behavior is also known as bubbling, a mechanism to remove excess water from nectar (or dehydrate nectar) resulting in nectar with higher sugar concentrations.
Portman et al. (2021) summarized five documented reasons bees concentrate nectar:
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Help prevent spoilage during long-term storage by social Apidae, for example Bombus and Apis, that store nectar in their nests.
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Increase the nutritional value of larval provisions by incorporating higher concentrations of sugars with the pollen.
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Dehydrate the nectar to allow more storage in the crop.
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May help bind together pollen grains with concentrated or more viscous nectar for bees that mix nectar with pollen loads on their corbiculae or scopae.
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Can help with nest thermoregulation, particularly for social bees, by removing excess water in nectar.
An Andrena geranii female concentrates nectar while perching on foliage.
© Michelle Orcutt
A Lasioglossum female concentrates nectar while perching on foliage.
Participatory Science Opportunities
iNaturalist Project: Bees Concentrating Nectar
This project compiles observations of bees concentrating nectar with their mouthparts (also known as "bubbling"). The project is limited to pictures where a nectar bubble is clearly visible. Observations contributed to the project will help with research conducted by Dr. Zach Portman and Dr. John Ascher and may help inform how widespread this behavior is and why bees do it.
Slumber Parties (Roosting Aggregations)
Most female bees spend the night in their nest. Adult males, however, do not return to their natal nest after emergence and therefore spend their days and nights in the landscape. Some male bees spend the night by themselves in a flower or clutching the underside of a flower or leaf. Similarly, cleptoparasitic (cuckoo) bees do not have nests, so they spend the night clasping onto plants or stems with their mandibles. In contrast, many species of male bees (and wasps), particularly those belonging to the families Apidae, Megachilidae, and Halictidae, congregate to form overnight roosting aggregations. Amazingly, some accounts of roosting sites demonstrate that the same location/vegetation is used for multiple years by each subsequent generation.
Cleptoparasitic (cuckoo) bees such as this Nomada banksi often roost singly on vegetation.
For nesting bee species, these overnight roosting aggregations or "slumber parties" are usually all-male although there are accounts of single females roosting on vegetation near their nests, rather than in their nests. These slumbler parties, composed of many males, are typically initiated in late afternoon or early evening for a one- to two-week period. For example, Melissodes bimaculatus is active in early July; in late afternoon, many males gather in a specific site on vegetation, clasp leaves or stems with their mouthparts, then spend the night in this immobile position. Each morning after sunrise, they disperse for the day, only to gather again that evening in the same spot. One benefit proposed for these gregarious sleeping aggregations is they offer protection from predators.
A roosting aggregation of Melissodes bimaculatus males.
Melissodes bimaculatus males jockey for a spot in the roosting aggregation.
Pollen Collection Behaviors
Buzz Pollination (Sonication)
Most flowers have anthers that, when fully developed, have openings from which pollen is passively released. The openings are often narrow slits along the length of the anthers. Some flowering plants have inverted anthers with valves or pores, and pollen must be actively released. In addition to plants with inverted anthers, nectarless plants are often buzz pollinated by native bees, for example, Rosa blanda (smooth wild rose), Tradescantia ohiensis (Ohio spiderwort), and Geum triflorum (prairie smoke). To overcome the difficulty of collecting pollen from inverted anthers with pores, many bees have developed a mechanisum known as sonication or buzz pollination. To extract the pollen from these flowers, bees employ this mechanism by detaching their wings from their flight muscles while simultaneously clasping the anthers with their forelegs or mouthparts, then vibrating the flight muscles in their thorax at a high frequency, to shake the pollen out of the pores.
Sonicating flowers releases a large quantity of pollen, so for bees that are capable of sonication, it is an efficient skill that can yield them a quantity of pollen equivalent to that of numerous flower visits without sonication. Bees known to buzz-pollinate flowers include Bombus (bumble bees), Xylocopa (large carpenter bees), Andrena (mining bees), Halictus (sweat bees), Lasioglossum (small sweat bees), and Agapostemon, Augochlora, Augochloropsis, and Augochlorella (metallic green sweat bees). Ericaceous (blueberries, cranberries), Solanaceous (tomato, eggplant, pepper), and some Fabaceous plants such as Chamaecrista fasciculata, require buzz pollination.
A pair of Augochloropsis females buzz-pollinate a Rosa blanda flower.
A Bombus griseocollis female buzz-pollinates cultivated blueberry flowers.
An Augochloropsis metallica female buzz-pollinates a Rosa blanda flower.
A Preliminary List of Buzz-Pollinated Plants in Minnesota
Plant Type | Plant Family | Scientific Name | Common Name | Notes | Manual sort |
|---|---|---|---|---|---|
Perennial | Commelinaceae | Tradescantia bracteata | Long-bracted Spiderwort | Nectarless | 0d |
Perennial | Commelinaceae | Tradescantia occidentalis | Spiderwort | Nectarless | 0d8 |
Perennial | Commelinaceae | Tradescantia ohiensis | Ohio Spiderwort | Nectarless | 0dg |
Shrub | Ericaceae | Andromeda polifolia | Bog Rosemary | Poricidal anthers | 0do |
Shrub | Ericaceae | Arctostaphylos uva-ursi | Bearberry | Poricidal anthers | 0e |
Shrub | Ericaceae | Chamaedaphne calyculata | Leather-leaf | Poricidal anthers | 0e8 |
Shrub | Ericaceae | Chimaphila umbellata | Pipsissewa | Poricidal anthers | 0eg |
Shrub | Ericaceae | Empetrum nigrum | Black Crowberry | Poricidal anthers | 0eo |
Shrub | Ericaceae | Epigaea repens | Trailing Arbutus | Poricidal anthers | 0f |
Shrub | Ericaceae | Gaultheria hispidula | Creeping Snowberry | Poricidal anthers | 0f8 |
Shrub | Ericaceae | Gaultheria procumbens | Wintergreen | Poricidal anthers | 0fg |
Shrub | Ericaceae | Gaylussacia baccata | Black Huckleberry | Poricidal anthers | 0fo |
Perennial | Ericaceae | Moneses uniflora | One-flowered Pyrola | Poricidal anthers | 0g |
Perennial | Ericaceae | Orthilia secunda | One-sided Pyrola | Poricidal anthers | 0h |
Perennial | Ericaceae | Pyrola americana | Round-leaved Pyrola | Poricidal anthers | 0i |
Perennial | Ericaceae | Pyrola asarifolia | Pink Pyrola | Poricidal anthers | 0j |
Perennial | Ericaceae | Pyrola chlorantha | Green-flowered Pyrola | Poricidal anthers | 0k |
Perennial | Ericaceae | Pyrola elliptica | Shinleaf | Poricidal anthers | 0l |
Perennial | Ericaceae | Pyrola minor | Small Shinleaf | Poricidal anthers | 0m |
Shrub | Ericaceae | Vaccinium angustifolium | Lowbush Blueberry | Poricidal anthers | 0n |
Shrub | Ericaceae | Vaccinium caespitosum | Dwarf Bilberry | Poricidal anthers | 0o |
Shrub | Ericaceae | Vaccinium macrocarpon | Large Cranberry | Poricidal anthers | 0p |
Shrub | Ericaceae | Vaccinium myrtilloides | Velvet-leaf Blueberry | Poricidal anthers | 0q |
Shrub | Ericaceae | Vaccinium oxycoccos | Small Cranberry | Poricidal anthers | 0r |
Shrub | Ericaceae | Vaccinium uliginosum | Alpine Bilberry | Poricidal anthers | 0s |
Shrub | Ericaceae | Vaccinium vitis-idaea | Ligonberry | Poricidal anthers | 0t |
Annual | Fabaceae | Chamaecrista fasciculata | Partridge Pea | Nectarless | 0u |
Perennial | Orobanchaceae | Pedicularis canadensis | Wood Betony | 0v | |
Perennial | Orobanchaceae | Pedicularis lanceolata | Swamp Lousewort | 1 | |
Perennial | Primulaceae | Dodecatheon amethystinum | Jeweled Shooting Star | Nectarless | 14 |
Perennial | Primulaceae | Dodecatheon meadia | Prairie Shooting Star | Nectarless | 18 |
Perennial | Primulaceae | Primula mistassinica | Mistassini Primrose | Nectarless | 1c |
Perennial | Rosaceae | Geum triflorum | Prairie Smoke | 1g | |
Shrub | Rosaceae | Rosa arkansana | Prairie Rose | Nectarless | 1k |
Shrub | Rosaceae | Rosa blanda | Smooth Wild Rose | Nectarless | 1o |
Shrub | Rosaceae | Rosa woodsii | Wood’s Wild Rose | Nectarless | 1s |
Perennial | Rusaceae | Polygonatum biflorum | Smooth Solomon’s Seal | 2 | |
Perennial | Rusaceae | Polygonatum pubescens | Hairy Solomon’s Seal | 2g | |
Annual | Solanaceae | Leucophysalis grandiflora | Large False Ground Cherry | Nectarless | 3 |
Perennial | Solanaceae | Physalis heterophylla | Clammy Ground Cherry | Nectarless | 3g |
Perennial | Solanaceae | Physalis longifolia | Long-leaf Ground Cherry | Nectarless | 4 |
Perennial | Solanaceae | Physalis virginiana | Virginia Ground Cherry | Nectarless | 6 |
Annual | Solanaceae | Solanum rostratum | Buffalo Bur Nightshade | Nectarless | 8 |
Annual | Solanaceae | Solanum ptychanthum | Black Nightshade | Nectarless | g |
An image illustrating rasping behavior by an Anthophora terminalis female visiting a Penstemon digitalis flower.
In addition to or in lieu of buzz pollination, female bees have a number of pollen gathering behaviors that they employ while visiting flowers. Portman et al (2019) classified these pollen gathering behaviors into the following categories:
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scraping with the extremities - using their mouthparts or legs to remove pollen;
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rubbing the body and/or scopa(e) against the anthers while maintaining continuous contact;
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tapping - a rapid up and down motion of the abdomen directly on the anthers;
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rubbing the face - continuous contact between the anthers and face;
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rasping - rubbing or vibrating the back of the thorax against the anthers.
Thermoregulation
Bees have the ability to regulate their body temperature to be able to fly and forage in cool temperatures, and incubate eggs in eusocial nests. The warming of a bee's body temperature is achieved by contracting the thoracic (flight) muscles. These muscle contractions generally do not result in any motion by the bee. A bee perches on the ground or on an object, and depending on the temperature differential between the body and air temperature, can warm up in a few to several minutes. Bees also warm up by basking in sunny microhabitats close to the ground or on a object such as a rock that absorbs the sun's heat. Another microhabitat where bees warm up is provided by dish- or cup-shaped flowers that track the sun. By changing the flower's position throughout the day to continuously face and track the position of the sun, a mechanism termed heliotropism, the flower becomes an attractive and warm microhabitat for bees to forage and sustain their foraging and flight temperature. Heliotropism is particularly important in early spring when air temperatures are cool, limiting a bee's foraging ability.
The quantity and density of hairs on a bee can also help with thermoregulation. For example, Heinrich and Esch (1994) noted that the hairs on a bumble bee can help cut their heat loss in half in cold environments. Many solitary bees are small and sparsely haired, limiting their abilty to sustain heat in cold environments.
Egg incubation is critical in bumble bee nests. Because new bumble bee gynes establish their nests in early spring, they need to keep their initial mass of eggs warm prior to hatching. Similar to a bird incubating eggs, the gyne wraps her abdomen over the pollen mass and eggs, keeping them warm. To do so, she must transfer heat produced by contracting her flight muscles from her thorax to her abdomen.
Like cold environments, hot environments that result in heat stress can also limit a bee's physiological functions such as motor function. Corbet and Huang (2016) determined that for solitary female bees to shed excess heat accrued while visiting fowers, they offload the heat while flying where the air temperature is lower than in flowers. Because of their physical size (being smaller and generally less hairy than bumble bees, for example) they are able to cool down more rapidly than would a large, hairy bee while flying. This cooling strategy, like the warming strategies employed above, comes at an energetic cost and decreased time spent foraging.
Early spring-blooming American Pasqueflower (Anemone patens) flowers create a warm microhabitat by having bowl-shaped flowers and by continuously turning throughout the day to face the sun. This microhabitat can help bees thermoregulate, sustaining temperatures required for flight and foraging.
A Bombus bimaculatus gyne visits Salix discolor (pussy willow) flowers in early spring. Prior to flying on cold spring days, she contracts her flight muscles to warm up her body temperature.
Explore Bee Families
Citations and Further Reading
Alcock, J. (1998). Sleeping aggregations of the bee Idiomelissodes duplocincta (Cockerell)(Hymenoptera: Anthophorini) and their possible function. Journal of the Kansas Entomological Society, 74-84.
Corbet, S. A., & Huang, S. Q. (2016). Small bees overheat in sunlit flowers: do they make cooling flights?. Ecological Entomology, 41(3), 344-350.
Danforth, B. N., Minckley, R. L., & Neff, J. L. (2019). The solitary bees: biology, evolution, conservation. Princeton University Press.
Evans, H. E., & Linsley, E. G. (1960). Notes on a sleeping aggregation of solitary bees and wasps. Bulletin, Southern California Academy of Sciences, 59(1), 30-37.
Heinrich, B., & Esch, H. (1994). Thermoregulation in bees. American Scientist, 82(2), 164-170.
O'Neill, K. M., Evans, H. E., & Bjostad, L. B. (1991). Territorial behaviour in males of three North American species of bumblebees (Hymenoptera: Apidae, Bombus). Canadian Journal of Zoology, 69(3), 604-613.
Portman, Z. M., Ascher, J. S., & Cariveau, D. P. (2021). Nectar concentrating behavior by bees (Hymenoptera: Anthophila). Apidologie, 1-26.
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.
Portman, Z. M., Orr, M. C., & Griswold, T. (2019). A review and updated classification of pollen gathering behavior in bees (Hymenoptera, Apoidea). Journal of Hymenoptera Research, 71, 171-208.
Tengö, J. and Bergström, G. (1977). Cleptoparasitism and odor mimetism in bees: do Nomada males imitate the odor of Andrena females? Science, 196(4294), 1117-1119.
Page Photography and Video Credits
Heather Holm
Joel Gardner CC BY-ND-NC 1.0 (Melittidae)
Michelle Orcutt (Lasioglossum concentrating nectar video)