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Bumble Bees: Nesting and Overwintering

"A brown-belted bumble bee sits atop a cluster of orange eggs in a nest "Brown-belted Bumble Bee in a nest. (Photo: Kent McFarland / Flickr.)

 

Discovering a bumble bee nest, or unearthing a queen bumble bee from hibernation is an exciting experience! Many researchers have spent hours looking for these elusive components of bumble bee biology with limited success. If you’re here, it is likely that the bumble bees have found you! The good news is that this likely means you’re doing a good job of creating habitat for pollinators, kudos! We also understand that finding a busy nest of bees near family or property can be unnerving, or frightening. If you’re looking for more information on what you’ve found, or how to negotiate the situation, this page will provide details on overwintering queen bumble bees and bumble bee nests, including background biology to help you better understand the situation and provide some options for moving forward safely. 

Note: Xerces Society staff do not relocate bumble bee nests and do not provide specific advice other than what you can read here. We provide this information for educational purposes only. If you decide to move a nest, you do so at your own risk.

 

Jump to Handling Bumble Bee Nests

Jump to Overwintering Queen Bumble Bees

 

Basics of a Bumble Bee Nest

While there are many different species of bumble bees (ca. 50 in North America), and their biology differs by climate and habitat, generally bumble bees have an annual life cycle. This means that a nest, founded by a single queen who lives for ~ 1 year, is active for one season. While the life cycle is continuous, with each foundress queen overlapping with her queen offspring in the fall, we can imagine the “start” of the life cycle to begin when queens emerge from hibernation. Each spring, queen bumble bees emerge from hibernation and will spend a few weeks foraging and searching for a nest location. Bumble bees like to nest in pre-existing cavities that provide insulation and protection from the elements, such as old rodent burrows, bunch grasses, and as you may have found out— man-made structures, like bird houses, insulation, or even the cotton batting of old furniture. Because bumble bees use existing cavities, and do not create or dig their nests, they will not cause physical damage to your property (other than lightly soiling the cavity where they’ve built a home). Unlike wasps and carpenter bees they do not eat or chew wood. If you’d like them to avoid the area in the future, simply block the entrance hole in late fall (when you no longer see activity).

After establishing a nest location, the queen will spend the next month gathering food resources, and building waxen pots that she fills with pollen upon which she lays her eggs. After she lays her eggs, she alternates between gathering food and egg incubation. The hatched eggs feed on the pollen and nectar provided by the queen and go through several instars as they grow. Like caterpillars, bumble bee larvae go through complete metamorphosis and transform from the colorless “worm” that emerges from laid eggs to a colorful and fuzzy adult bumble bee over 4-5 weeks. Once the larvae pupate and are no longer feeding, the queen will lay a second batch of eggs. The first batch of offspring are female workers and will gradually take over the foraging duties and nest maintenance so the queen can focus on egg laying; once there is an established worker caste, the queen no longer leaves the nest. 

Black-tailed Bumble Bee nest. (Photo:Kimberly Adams.)

Rolling into summer, many colonies typically reach their peak size and contain anywhere from 50-500 workers (nest size is species and habitat dependent). The bees we typically encounter, unless you have found a nest, are worker bees who are out visiting flowers or flying to and from their nest. Importantly, even the largest of nests will likely only produce light to moderate traffic around the nesting site; nothing like you might see around a honey bee hive.

As the colony continues to grow and build resources, the queen will switch from rearing worker bees to focusing on the development of the  reproductive members of the colony—males and gynes (next year’s queens). The number of males and gynes produced by a colony will depend on the species and available resources available (some nests never reach this stage, others will only produce males), but can vary from zero to dozens. The males and gynes leave the nest to mate (with members of a different colony). While the gynes will return to the nest for protection and to share nest resources with their sisters, the males do not return (and can often be found sleeping on vegetation in late summer) and expire within a few weeks.  Back at the nest, the foundress queen and worker bees will also begin to die off. Meanwhile, the newly-mated queen will scour the landscape for any remaining plants in bloom to build up fat reserves for the winter, while searching for a place to overwinter.

Once a suitable location is found, the newly-mated queen will burrow down into the earth and enter a hibernation-like state until the following spring. The overwintering phase is arguably the most vulnerable step of the bumble bee life cycle, as she must survive in order to begin a successive colony the following spring. Yet, the specifics of overwintering—like site selection, preference of natural materials, depth and size of burrows, survival rates, and much more—are still largely unknown to scientists. See below for more information about overwintering queens.

 

Is it a bumble bee?

Make sure you are dealing with bumble bees and not carpenter bees. Carpenter bees often nest in wooden structures and look very similar to bumble bees: carpenter bees have shiny, hairless abdomens, whereas bumble bees have dense hair on their abdomen. Carpenter bees are solitary, meaning they nest alone, though during mating season you may find multiple males in the same area displaying territorial darting behaviour. While this darting behavior is intimidating, male bees cannot sting and are harmless to us. However, as their name implies, carpenter bees build their nests in wood and can cause structural damage. If you find a large aggregation of carpenter bees in your home, you may want to consult a home contractor. You can also look on the internet for ways to encourage them to nest elsewhere. 

 

"Western bumble bee nectaring on a pink thistle" "Large carpenter bee on a green leaf"(Photos: Bumble Bee Watch / Jeanne Dammarell [left] and Bumble Bee Watch / Bob Brackpool [right].)
 Bumble Bee (Left Image)Carpenter Bee (Right Image)
AbdomenVery hairySmooth, shiny
Hind LegSmooth, hairless section called a pollen basket (corbicula)Very hairy (scopa)
HeadSmaller, hairyLarger, less hairy
NestingUtilizes pre-existing cavityBores hole in wood

 

 

 

 

 

 

 

Handling Bumble Bee Nests

In the description of bumble bee nests above, you learned that bumble bees are annual organisms and that the nest is only active from spring through summer. During the rest of the year, the colony is survived by a solo queen bee hibernating below ground, in a different location. 

In terms of handling a nest, this annual life cycle makes things much easier because the nest will die of natural causes come

fall (or sooner as different bumble bees differ in their timing of emergence and senescence) and it is unlikely that the same nest will be occupied in the following year. For these reasons (short duration and limited traffic at the nest), we suggest that you do not attempt to relocate a nest.

However, if you have a bumble bee nest thriving in an undesirable area, there are a few options for you to proceed safely. Whichever route you choose, you should be mindful of approaching an active nest. While bumble bees are generally docile creatures, they can sting and when threatened will defend their home.

 

"Bumble bee nest box showing a bumble bee nest in fiberglass insulation with adults and eggs"
   Bumble bee nest box. (Photo: David Jones.)

Option 1 (preferred): Wait it Out

Opting to leave the nest alone and allowing the colony to senesce on its own is the easiest and smartest option, and will create the least disturbance. If the nest is not in the way, or you can find a way to temporarily change traffic patterns to avoid the area, the bees will continue to thrive in their chosen location. It should only be a few weeks of disturbance to your usual patterns, and you may even learn a thing or two about your new residents while helping to support native pollinators! 

If you have young kids (or are one at heart), bumble bee nests can be great opportunities  to learn about native bees and the importance of pollinators, while observing bumble bee nest behavior. Even when watching from afar you can learn about their foraging and emergence patterns (are they different at different times of day/year?). You could also create a sign as a safety measure and to help educate your friends and neighbors. This is also an opportunity to participate in a community science project, and submit a nest sighting to Bumble Bee Watch to help scientists learn more about bumble bee nests.

 

Option 2: Create a Barrier Around the Nest

Creating a barrier around the nest is  a common route taken by those wanting to protect young children or pets in areas that cannot be avoided. Oftentimes, creating a barrier offers enough protection, while also allowing the bees to complete their life cycle. 

To build a barrier, you can secure chicken wire or garden netting with a few stakes, or stack wood or stones around the nest—anything that still allows the bees to enter and exit their nest while keeping kids or pets from getting too close. The safest time to construct a barrier is at night or very early in the morning when bees are least active. Even so, bees are more inclined to sting if you are near their home, so cover up your skin with thick layers (rain pants and jackets provide good protection) and wear long sleeves, pants, and gloves. You may even use duct tape to seal the cuffs of your sleeves and pant legs to prevent bees from accidentally entering your clothing.

 

Option 3: Reroute Nest Entrance(s)

It is not unusual for bumble bees to nest under decks or in an area with exposed housing insulation and their nest entrance becomes problematic for the homeowner. If you can locate (or create) an alternate route for the bees to enter their nest, consider plugging the problematic entrance rather than moving the nest. For example, if the bees are entering their nest through a hole in the top of your deck and you’re worried about stepping on them or getting stung by accident, plug that hole and the bees will be encouraged to find another way out (you may want to dig/create a small hole for them before you do this to provide access to the nest in a more desirable direction).

 

Option 4 (last resort): Relocate Entire Nest and Substrate

NOTE: Xerces Society staff do not move bumble bee nests and we provide this information for educational purposes only. If you decide to move a nest, you do so at your own risk.


Bumble bees have been known to nest in birdhouses and various items stored in sheds or barns, such as tarps, patio furniture, compost piles, or unused flower pots. If the item the bees have chosen to nest in is mobile, move the entire nest to a more desirable location. If the nest is underground, relocation will be nearly impossible as entrance tunnels can sometimes be several feet long. Remember, bumble bees will only be utilizing their nest and substrate until fall at the longest, so if they have chosen to nest in a tarp or trash bin that you need, consider borrowing one from a neighbor while the bees complete their life cycle.

If you decide to move the nest, have a clear plan in place that lays out how and where you intend to relocate the nest before physically picking up the nest. The safest time to move the nest is at night when temperatures are low, because bees are less active in cooler temperatures and will likely be less agitated than if moved during their “work hours.” Also, if you move the nest during the day, any bees that are out foraging will not be able to find the new nest location, and will likely die. The first step in any nest relocation should involve plugging the entrance/exit hole. Since you will likely be doing this at night, it is best to make your plan during the day so that you know what obstacles may be in your way. A red light will be unlikely to agitate the bees (they don’t see red very well) and may help you to see better. Rather than transporting the nest in the open, it is best to transport it in a large plastic bin or cardboard box. Otherwise, individual bees may fly out of the nest during relocation, creating a threat to you, and potentially get lost in the process.

Bees are more inclined to sting when they feel threatened and will defend their home, so cover up your skin with thick layers and wear long sleeves, pants, and gloves. You may even use duct tape to seal the cuffs of your sleeves and pant legs to prevent bees from accidentally entering your clothing.

 

"A series of 6 images showing different human-made structures utilized by bumble bees as nesting locations, (1) under a deck, (2) in fabric stored in a shed, (3) in a cardboard box, (4) in a stored horse saddle, (5) in a birdhouse, and (6) in a cart of dried hay under a plastic lid"Bumble bees prefer to nest in pre-existing cavities, such as old rodent burrows, that offer insulation and protection from the elements. As shown in the photos above, they are quite advantageous when it comes to man-made cavities and have been observed nesting (1) under a deck, (2) in fabric stored in a shed, (3) in a cardboard box, (4) in a stored horse saddle, (5) in a birdhouse, and (6) in a cart of dried hay under a plastic lid. (Photos courtesy of Bumble Bee Watch participants: (1) Warren Biro; (2) Christina Schilling; (3) Danielle Hatton; (4) Ann Puddicombe; (5) Patty Allen; and (6) Julie Thornburg).

 

Option 5: Call an Expert

If none of the above options fit your needs, contact your local University’s Extension office and speak with the entomologist on staff. Many communities have a local beekeeper group who may also know how to provide assistance. If a professional service is contracted, like an exterminator, it is likely that they simply kill the nest.

 

Share Your Nest Observation!

Whether you choose to move the nest or not, please take a moment to submit your nest sighting through Bumble Bee Watch! By submitting a photo of the nest and a few additional habitat details, you are contributing to a large database of bumble bees in the United States and Canada that researchers use this information to improve conservation efforts. To check out nest observations submitted by others visit the Nest Gallery, you may be surprised at some of the locations bumble bees choose to nest!

You may also use Bumble Bee Watch to submit photos of bumble bees you observe while on a hike, in the garden, or anywhere else. Try the Bumble Bee Watch app (Apple or Android) for submitting photos while on the go!

 

Overwintering Queen Bumble Bees

A lucky gardener might be digging around in the dirt during fall or winter only to discover that a queen bumble bee has decided to take up residence during the cold seasons. If you’ve found yourself in this uncommon situation, there are a couple of ways to move forward and support the queen.

The first consideration is time of year and whether or not nights of frost are still expected. If spring has arrived and flowers are in bloom, place the queen in a safe, sunny location and allow her the space to “wake up” and adapt to her surroundings. If, however frost is still in the forecast, your best bet is to gently cover her back up using the same material and hope that she will re-enter hibernation. Come spring, the queen will hopefully “wake up” and crawl to the surface. Be sure not to pack the soil too much and avoid using weed barriers that may trap the queen underground.

If spring has not sprung, and the queen seems distressed—lots of audible wing vibrations—or you attempt to relocate her to a new area, there is a chance the queen will not re-enter the hibernation-like state. In this situation setting, if spring has sprung, place her in a safe, sunny area. If spring has not arrived, or there are still expected nights of frost, you can try to gently place her back in the substrate you found her in or attempt to rear her indoors until spring arrives. To learn more about rearing bumble bees at home, see Befriending Bumble Bees: A Practical Guide to Raising Local Bumble Bees.

No matter which route you take in assisting the unearthed queen, we hope you will take a moment to submit your queen bumble bee observation. As stated above, the habitat requirements of overwintering queens are still largely unknown. By sharing your observation(s), you’re contributing to a growing dataset of observations from all over the country! As more information is gathered through these small-but-mighty submissions, our ability to conserve and support bumble bees and their habitat will only grow stronger.

To go one step further, you can take part in an active effort to search for queen bumble bees by participating in Queen Quest! Launched in 2019 by a group of bumble bee researchers, this nationwide project aims to increase our understanding of overwintering queens. Queen Quest begins each year in fall and runs through winter. To sign up, gather a small group of friends and learn the simple protocol outlined on www.QueenQuest.org.

 

Further Resources

Creating Nesting and Overwintering Habitat

Join a Bumble Bee Community Science Project

Pollinator-Friendly Plant Lists

Conserving Bumble Bees

Resources