Navigate / search

Officially endangered: the rusty-patched bumble bee

It’s official: the US Fish and Wildlife Service has listed the rusty-patched bumble bee, Bombus affinis, as an endangered species. This bee, in the family Apidae, is the first insect from the continental United States to make the list. Last year, seven species of Hylaeus were the first bees to make the list, but they occur only in Hawaii.

Like many things that were once abundant such as bison and passenger pigeons, it was easy to take the rusty-patched bumble bee for granted. It was once a common sight in eastern North America, occurring in 28 states and 2 provinces. But populations began to crash in the mid-1990s. The most recent data, collected in the early 2000s, show small populations remaining in only 13 states and Ontario, a decrease in range of about 87%.

Small populations lose genetic variability

Since no thorough counts have occurred since the early 2000s, populations are likely even lower. In fact, very few colonies have been spotted in recent years. When colonies are few and far between, outcrossing between non-related colonies is less likely to occur and inbreeding increases. Loss of vigor, often called inbreeding depression, makes the colonies more prone to disease, stress, and poor nutrition among other things.

Since accurate data on insect populations and distribution was not a priority in the past, little data is available to show trends over time. Many entomologists suspect that the number of rusty-patched bumble bee colonies was declining long before it came to anyone’s attention.

A large bee with a short tongue

The rusty-patched bumble bee is one of the large bumble bees. According to Bumble Bees of North America (2014) it is a short-tongued species that prefers to live in prairies, woodland, marshes, parks, urban gardens, and agricultural areas. They prefer to nest in abandoned burrows that once belonged to chipmunks or rabbits.

The rusty-patched bumble is polylectic, meaning it forages on a wide range of flowering plants. Depending on the local climate, individuals may be seen from April through October, but it is most abundant in July and August.

Habitat loss is crucial

According to a report by the Natural Resources Defense Council, the primary reason for the population decrease is habitat loss. But other factors such as the disease Nosema bombi, which has spread from commercial bumble bee stocks, may have had a large impact.

Other detrimental conditions include heavy use of pesticides, habitat degradation, loss of forage, and climate change. Climate change causes mismatched timing between flowering plants and the bees that depend on them. It may also cause increased flooding that destroys underground burrows, and prolonged drought that can interfere with the food supply.

Ultimately, as colonies become more scattered, the dynamics of small populations—like inbreeding depression and large numbers of sterile males—causes what is known as an extinction vortex. An extinction vortex is easy to visualize: just imagine a population of any animal swirling around a drain until it finally disappears. As the number of individuals gets lower and lower, the remainder disappear faster and faster.

How can you help the rusty-patched bumble bee?

The US Fish and Wildlife Service lists three things that anyone can do to aid the rusty-patched bumble bee. But the most important thing to remember is that these three items can help any population of pollinator, no matter where you live.

  • Plant flowers that will bloom from early spring through fall.
  • Provide a safe place for overwintering. In other words, leave some areas of your yard undisturbed all year long. That means no tilling, no raking, no removing dead stems.
  • Avoid pesticides, especially insecticides and herbicides.

According to Bumble Bees of North America, the rusty-patched bumble bee prefers flowers in the following families: Aesculus, Agastache, Dalea, Eupatorium, Helianthus, Impatiens, Lonicera, Monarda, Prunus, Solidago, and Vaccinium. Do your part for the remaining pollinators and plant a wide diversity of flowers.

Honey Bee Suite

The rusty-patched bumble bee has been listed as endangered by the US Fish and Wildlife Service.
The rusty-patched bumble bee has been listed as endangered by the US Fish and Wildlife Service. Photo by Dan Mullen. The original photo can be seen on Flickr.





Where have all the flowers gone?

“Where have all the flowers gone?” is a folk song written by Pete Seeger in 1955. Since then, the song about war and death has been recorded by dozens of artists in many languages, and additional verses have been added by various performers. In 2010, the New Statesman chose the piece as one of the top political songs of all time.

Back then the words “bee” and “nutrition” were rarely heard in the same sentence. Bee nutrition was something you had no reason to worry about. Bees ate what they preferred and thrived on it. Although bees back then had to duck pesticides, their food supply was varied, plentiful, and nutritious. Meadows and farmlands were abuzz with bumbles, carpenters, masons, sweat bees, and honey bees.

In a sense, the answer to “Where have all the flowers gone?” remains political even when you are discussing bees. Not political in the sense of a particular party or nation, but political in the sense of how we human beings elected to care for our planet. Humans have consistently put their own needs before that of the environment and we are paying the price. Species around the globe are going extinct at a terrifying rate leaving us with fewer and fewer resources.

How far must they fly?

Of all the bee species, honey bees are probably the best able to handle the lack of suitable forage. Honey bees have an incredible foraging range which can be measured in miles. In lean times, honey bees have been known to cover up to five miles. Simple math will show you that a circle with a radius of 5 miles covers roughly 50,000 acres.

On the other hand, most of the solitary bees travel short distances, some only a few hundred feet from the spot where they were born. A circle with a radius of 300 feet, for example, covers only about 6.5 acres. For many native bees, a Costco parking lot is a vast desert, both barren and dangerous, that it will never cross.

Lots of honey does not assure good nutrition

The pounds and pounds of honey your bees bring in can be deceiving. Is it possible for a colony with 50 pounds of surplus honey to be malnourished? Sounds crazy, but is it possible for an overweight teenager to be malnourished? The answer can be yes in either case.

All living things need a proper balance of nutrients in order to thrive. Crops are supplemented with compost or fertilizer just as dog food and rabbit feed are formulated to provide optimum growth. High energy foods such as sugar and starch do not supply the amino acids, proteins, vitamins, minerals, and micronutrients needed by living things. As such, it is very possible for a colony heavy with honey to be light on good nutrition. Remember, it’s the pollen that keeps the hive alive.

Not all pollen is created equal

But even pollen has its limitations. Just as one vegetable cannot supply all our nutritional needs, one pollen type cannot supply a bee’s nutritional needs. Like everyone else, bees must eat a varied diet.

Many aspects of modern life have made the flowers disappear and compromised bee health. I can’t name them all, but here a few of the most obvious.

Where the flowers went

Herbicides: Herbicides kill the flowering plants that once lined roads, playgrounds, orchards, and fields. This destroys a valuable source of pollen, nectar, and bee habitat.

Invasive Species: Nature abhors a vacuum, so after you kill the native vegetation with herbicide, the invasive weeds have a perfect spot to take root. With no competition from local plants, the invasives become a type of monoculture.

Monoculture weeds: Like monoculture crops, monoculture weeds have lots of pollen, but of only one type. Worse, instead of having dozens of different plants that bloom at different times and provide food over a long period, you have a single species that blooms all at a once. After that, there is nothing left for bees to eat.

Ornamental Plantings: Ornamental plants are often imported and since our local bees didn’t evolve along with them, the bees may not like their pollen.

Hybrid Varieties: Hybrid varieties may offer little or no pollen because the plant breeders who developed them were looking for traits other than nutritional pollen. They may have been breeding for color, winter hardiness, drought tolerance, disease resistance, or some other trait that appeals to humans, not bees.

Climate Change: Regardless of what causes climate change, climate change causes trouble. In some cases, bees and flowers get out of sync with each other. Plants respond more quickly to temperature changes and may bloom early, but bees come out of hibernation after the requisite number of days or months. In some situations, flowering of their favorite species is over before the bees emerge.

Habitat Loss: Flowers don’t thrive in parking lots, stadiums, airports, freeways, shopping malls, or cityscapes. Sure, honey bees can navigate the cites, but that’s largely due to their foraging range. Native bees don’t have much of a chance in these places, especially the solitary ground-dwellers, which are the vast majority of bee species.

Habitat Fragmentation: Small plots of land often don’t have enough flowering plants to support the bees that live there, but additional plots may be too far away for the bees to travel.

Agricultural Practices: Growers used to cut forage crops such as clover and alfalfa (lucerne) after flowering, a practice which provided lots of bee feed. But in modern times, forage crops are cut just before flowering, so both the pollen and nectar are lost.

Lawns of Grass. You often hear that lawns cover more acreage than any other crop in North America. I don’t know if that’s true, but it’s close. Unfortunately, there is very little about a modern lawn that is good for bees: no forage, no open ground for nesting, no nesting materials, just lots and lots of chemicals.

Evergreen Landscapes: Both commercial and residential landscapers have turned to evergreen plants and shrubs because they stay green and don’t shed, but most add little to the bee diet. One landscaper working in front of a bank told me that evergreens are great because they keep bees from scaring the customers away. So sad.

Planting flowers is the best way to help bees

So when people ask how they can help the bees, tell them to plant flowers. It’s the best thing anyone can do for our pollinators. Flowering trees produce lots of forage, but even small gardens and planters can help. Heirloom and open-pollinated varieties produce the best pollen, but a selection of plants with a wide spectrum of bloom times is the goal. If space is an issue, concentrate on those things that bloom in late summer and early fall—the most critical time for bee nutrition.

Honey Bee Suite

Bee on basil. The flowers are gone.
Since many of the native flowers are gone, we need to plant for the pollinators. Pixabay public domain photo.

What are winter bees and what do they do?

As beekeepers, we tend to underestimate the importance of winter bees. We are especially unconcerned late in August, just when the colony is on the brink of producing these winter wonders. On a sultry August afternoon when the cat is long and the air is too hot to move, the next brew may seem more important than the next bee. But that next bee may be the one to shepherd your colony into spring, long after the brew is forgotten.

So what about winter bees makes them so important? And what makes them different from any other bee? According to Remolina and Hughes, winter bees are workers that emerge near the end of the foraging season [1]. Rather than living six weeks like most of their summertime sisters, winter bees may live six months, or even longer. These are the bees that determine whether our colony will survive the winter. And because of that, we beekeepers need to pay them more attention [2].

What makes a winter bee special?

The main difference between a winter bee and any other bee is the presence of enlarged fat bodies in the abdomen. According to Rosanna Mattingly in Honey-Maker, “the fat body puts together, stores, and breaks down not only fats but also proteins, carbohydrates, and other molecules.” [3] Fat bodies also produce vitellogenin, an amazing substance that allows a nurse bee to secrete brood food even in the absence of fresh pollen. Vitellogenin also enhances the immune system and increases lifespan.

Winter bees spend their lives within the nest where they care for the queen, help the colony with temperature regulation, and raise the brood that will inherit the colony in spring. Biologists believe that winter bees evolved as honey bees began to migrate into colder climates. In areas where cool temperatures prevented year-round collection of pollen, honey bee colonies needed a system that could see them through the shortage.

Winter bees can be considered a caste

Just as any fertilized egg can become a queen, so can any fertilized egg become a winter bee. Their genetics are identical. In fact, some authors refer to winter bees as a separate caste. A caste in the traditional sense is defined as “a physically distinct individual or group of individuals specialized to perform certain functions in the colony.” The winter bee caste is physically distinct because of the enlarged fat bodies, and those fat bodies have a special function. They produce large amounts of vitellogenin which can supplement or replace a winter pollen supply.

Winter bees are produced when pollen becomes scarce. Just as a queen can be raised by feeding a larva a special diet, a winter bee can be raised by feeding a larva a special diet. But the diet that triggers a winter bee is not extra rich like a queen diet, instead it is extra lean. Larvae fed a diet deficient in protein can trigger the development of winter bee traits [4].

Because winter bees are produced when pollen is lacking, winter bee production is dependent on local conditions. If you live in an area with plenty of summer rainfall, your winter bees will develop later than someone who has a significant summer dry spell. The important point is that pollen, not temperature, regulates winter bee development [5].

Without pollen, a colony is nothing

As any good beekeeper knows, pollen is the currency of a beehive. While nectar provides energy, pollen provides everything else. You cannot raise bees or children on sugar alone; you also need protein, fat, lipids, vitamins, minerals, antioxidants, and trace elements. Pollen contains all of these and more.

Without a diverse source of high-quality pollen, a colony will collapse. Such a colony cannot produce healthy offspring and cannot perform the many functions necessary for day-to-day life, let alone prepare for lean times.

However, everyday life in a bee colony is fraught with lean times. Pollen can become scarce during protracted wet weather, dry spells, and certainly over winter. Yet a colony does not store pollen on the same scale as it stores nectar. Most pollen storage is used almost as quickly as it is collected, so how does a winter colony survive?

Enter the winter bee

The answer lies within the winter bee. Although we think of pollen storage as occurring in the combs surrounding the brood nest, winter storage of protein actually occurs inside the winter bee. The enlarged fat bodies, along with enlarged hypopharyngeal glands, provide a vast storehouse for vitellogenin and other materials needed to produce brood food.

This hidden treasure is the reason a healthy colony can produce a batch of spring bees long after the last pollen flow has ceased and long before the new one begins.

Even winter bees have their limits

But just as a pollen cell is limited in size, so is a winter bee. As winter bees begin to feed brood, their fat bodies shrink and the glands produce less. Eventually they can run dry. In many situations, they have enough to get them into spring. But if conditions are bad, if a dry spring follows a harsh winter, the protein may eventually run out.

The possibility of running out has a lot to do with the strength of the colony going into winter, the amount and quality of stored food, the mite load, and the winter weather. For those reasons, many beekeepers find that a supplemental pollen source can make a world of difference in the strength of overwintered colonies.

In an interesting twist, Mattila and Otis found that feeding supplementary pollen to colonies in late summer or early fall did not boost the quantity of winter bees but merely increased the length of the normal brood rearing season [6]. This makes sense if you consider that that lack of high-quality brood food is what stimulates the production of winter bees. As long as good brood food remains available, normal “summer” bees will be produced.

Their findings suggest that supplemental feeding may be more beneficial after the winter bees have emerged. Many beekeepers follow this pattern, waiting until mid-winter before giving supplements. But even giving supplements early can have benefits because increasing the brood rearing season decreases the length of time winter bees need to survive.

Let’s not forget about Varroa mites

While we’re thinking of winter bees, remember that a weak or virus-infected winter bee will be useless to the colony. I cannot stress enough how important it is to have mites well under control before the winter bees emerge. If a winter bee starts life with a viral infection, that bee’s vitellogenin resources will be lost to the colony. In most of temperate North America that means mites need to be treated before the end of August.

Honey Bee Suite

[1] Remolina SC and KA Hughes. 2008. Evolution and mechanisms of long life and high fertility in queen honey bees. doi: 10.1007/s11357-008-9061-4.

[2] Some authors refer to winter bees as “diutinus,” which is a pretentious word for “long-lived.” Use diutinus if you want to be pompous, but use “winter bees” if you want to be understood.

[3] Mattingly RL 2012. Honey-Maker: How the Honey Bee Worker Does What She Does. Beargrass Press.

[4] Mattila HR and GW Otis. 2007. Dwindling pollen resources trigger the transition to broodless populations of ling-lived honeybees each autumn. Ecological Entomology. 32:496-505.

[5] Not everyone agrees on what triggers winter bee development. Other theories include the presence or lack of various pheromones in the brood nest.

[6] Mattila HR and GW Otis. 2007. Manipulating pollen supply in honey bee colonies during the fall does not affect the performance of winter bees. Canadian Entomologist. 139:554-563.

Winter bees in the snow.
Winter bees tucked in till spring. Pixabay photo.

Happiness is a mid-winter cleansing flight

Well, I don’t know if the bees are happy, but I certainly am. Whenever I see winter bees dart outside on a cold afternoon and drop a semi-solid parcel, I sigh with relief. I want to say, “See! You can do this! You can make it till spring, one day at a time.”

I’ve never liked the term “cleansing” flight because it reminds me of certain forms of human hocus-pocus. However, a quick flip through a dozen bee books reveals the term is generally accepted. A cleansing flight involves finding a day of relative warmth and brazenly leaving the hive for a quick bathroom break.

Such a trip is fraught with peril. Since bees cannot fly any distance when temperatures get down around 50°F (10°C), any bee traveling too far may get stiff from the cold and be unable to return home. Of course, not defecating is dangerous too. If bee feces builds up inside a hive, disease and unhealthy living conditions can threaten the colony. Although bees can wait long periods between cleansing flights, it seems probable that the shorter the wait, the better.

A mid-winter flight can be multi-purpose

In my hunt for definitions, I noticed that some people use the term “cleaning” flights for a mission that includes ridding the hive of debris. They claim that the removal of dead bees, parasites, wax bits, mouse feces, or defective larvae may be part of the mid-winter cleaning procedure.

Indeed, I have seen bees discard dead nestmates in winter, but from my own observations it seems that defecation is the major issue. Still, if a day is warm enough, a little light housekeeping may also be in order. Like everything else in beekeeping, what the bees dump on a given day will be highly influenced by local conditions.

Snow on the ground makes the entire cleansing process more visible. Sometimes a beekeeper seeing snow dotted with feces and dead bees becomes alarmed that a sudden crisis has befallen the bees. But cleansing, clearing, and cleaning are everyday processes that signal the colony is functioning normally. The snow merely illuminates their activities.

But why so many dead ones?

Beekeepers often claim that all the dead bees near a winter hive perished from prolonged exposure to the cold. Some say the dead are old bees that would have died soon anyway. Others say they were sick bees that sacrificed themselves for the good of the colony.

While each of these may be true, I think some of those dead bees are simply corpses that got dumped during housecleaning. In any case, the process is normal and serves a purpose. Whenever I see a few dead bees on the landing board or a sprinkling of dead bees on the snow, I am comforted by the idea that life in the hive is progressing according to plan.

Upper entrances may aid cleansing flights

On a side note, an article about winter management in The Hive and the Honey Bee (2015) by Currie, Spivak, and Reuter (p. 631) mentions that an arm of the winter cluster may move toward the entrance during the day and back at night. The authors speculate that this arm may be a corridor for bees that want to leave for a cleansing flight. In my own mind I picture this “arm” moving like an amoeba, flowing toward the entrance by day and retracting to the warmth of the cluster by night.

I find this idea fascinating because I have noticed over many years that my colonies with upper entrances in winter seem to do better than those without. I’ve always thought the reason was related solely to ventilation and moisture control. But now I wonder if easy, contiguous access to an exit that is kept relatively warm by an extension of the cluster, may facilitate timely bathroom breaks.

Compare the routes

Compare two bees. The first bee feels warm all the way to the door, flies out, defecates, and returns immediately to the warm extended arm of the cluster. The second bee travels in the cold air below the cluster, down through the depth of a brood box or two to get to the entrance where winter air is rushing in. She then takes her cleansing flight. But on her return, she is not greeted by warmth until she crawls back up through chilly brood boxes to reunite with the cluster.

The difference between the two routes could influence how many live and how many die. If I were a bee, I would opt for the quicker, warmer route.

Warm air leaves at the top

Warm air rises from the cluster (center) and keeps the candy board warm. Some heat escapes through the upper entrance, where the bees leave for cleansing flights. The heat near the ground escaped from my pump house. © Rusty Burlew

Beekeepers often challenge me on the use of upper entrances. Some claim that the bees crowd the upper opening in order to keep out cold drafts. But this never made sense to me because cold air does not flow into the upper entrance. Instead, warm air flows out.

Hot air rises. Cold air comes in through the lower entrance and is warmed by the cluster. As it warms it rises to the top of the hive and eventually leaves through the upper entrance or ventilation ports. Bees near that upper entrance are going to feel warm, not cold.

If you have any doubt about this, look at this thermal image I posted last week. In this image you can see the warm cluster in the middle of the hive and the warm air above it. You can also see warm air leaving through the upper entrance in front. Compare that area to the lower entrance at the landing board, which looks as cold as ice. The bees lallygagging behind the upper entrance must feel like they’re in a sauna, especially compared to any using the lower entrance.

It is my belief that the bees at the upper entrance are not there to block cold air but to luxuriate in warm air. And now I’m thinking they might be waiting for a hall pass as well.

Happy New Year to everyone, and thanks for another good year.


Do honey bees fly in the rain?

We’ve all seen honey bees fly in the rain. A light sprinkle or a short shower seems to have little effect on a foraging bee. On the other hand, a storm with heavy rainfall will keep the bees inside their hive. How do the honey bees decide when it’s safe to fly?

Based on a number of studies and a lot of anecdotal evidence, we know the honey bees are good at predicting the weather. In fact, honey bees seem to be more accurate than The Weather Channel when it comes to predicting rain. Not only can they predict it, but they can estimate its intensity. That is why a light drizzle may not influence their foraging patterns, but a heavy storm can keep them home.

Bad weather can trigger defensiveness

In a paper entitled “The Effects of Meteorological Factors on Defensive Behaviour of Honey Bees”1, researchers found that honey bees are more defensive during the approach of bad weather. The authors found that these spikes in defensiveness were largely the result of meteorological factors, including temperature, humidity, amount of solar radiation, wind speed, and barometric pressure.

Some beekeepers speculate that this increased defensiveness occurs because the bees “know” they must protect their food stores for the lean times ahead. Since honey bees are always “mindful” of the future, they increase the defense of their food stores.

Bees work harder before the storm

In a more recent study, “RFID Monitoring Indicates Honeybees Work Harder Before a Rainy Day”2, researchers tagged honey bees with RFID devices in order to track their foraging activity. They found that honey bees spent more time foraging on days immediately before a significant storm. Furthermore, they found that honey bees worked later into the evening on the day prior to a storm. Their theory is that the bees “predict” that food will be in short supply during the stormy weather, so they work extra hard before the storm hits.

These researchers point to prior studies, such as the one on defensive behavior, and speculate that honey bees predict the weather based on factors such as temperature, humidity, barometric pressure, and carbon dioxide levels. Many animals are able to predict inclement weather, just as we humans often do. We say things like, “Feels like rain” or “Smells like snow,” probably due to similar signals from our environment.

My own anecdotal evidence

Last year I inadvertently tested this theory with a lawn sprinkler. On a hot and sunny July afternoon I decided to water the lawn next to one of my hives. I set up a sprinkler which rained down on the hive and the surrounding grass. By all appearances, the bees were unperturbed by this turn of events, coming and going with pollen and nectar as usual. Even the accumulation of water on the landing board did not seem to upset them.

This type of observation lends credence to the idea that it is not the raindrops themselves that determine behavior, but the atmospheric conditions. When honey bees continue to forage during light showers and summer sprinkles, it is probably because the atmospheric indicators, the ones we can’t see, are telling the bees that it is safe to forage. “Get over it and keep working; there’s nothing to worry about!”

Behavior to watch for

In the future I intend to watch their behavior more carefully. Do bees foraging in the rain mean the weather will soon clear, or at least not get worse? Do unusually high levels of activity on a dry day mean a storm is near? Do drones behave any differently? And how about other species? Now that I’m thinking of this, I can’t wait till spring.

Honey Bee Suite

I often see bumble bees fly in the rain. I wonder if their standards are different? © Rusty Burlew

1Southwick, E.E. & Moritz, R.F.A. Int J Biometeorol (1987) 31: 259. doi:10.1007/BF02188929

2He, X.-J., Tian, L.-Q., Wu, X.-B. and Zeng, Z.-J. (2016), RFID monitoring indicates honeybees work harder before a rainy day. Insect Science, 23: 157–159. doi:10.1111/1744-7917.12298