My first book, The Beekeepers: How Humans Changed the World of Bumble Bees, has been released into the world. Due to the COVID-19 pandemic, we couldn’t have a huge book release party, but I did manage to have a very fun little party at home with my family.
My kids helped make decorations. I ordered a fancy cake from Q’s Cakes, a local bakery.
We wore silly hats, danced around, and had a great time. We eventually dug into the cake, which was almost too pretty to eat! Even our dog, Spirit, joined the festivities.
Huge thanks to my incredible agent, Stacey Kondla, and the wonderful team at Scholastic (Lisa Sandell, Amanda Shih, Keirsten Geise, and many others) for helping to create such a beautiful book.
Like all living things, bumble bees eventually die. A queen bumble bee lives for about a year. She hatches around late summer, hibernates over the winter, and emerges in spring to start her own nest of bees. By the end of the summer, she dies. Worker bees and male bees live for only several weeks. It’s a short life but a very busy one.
This week for my #BeeFactFriday I tweeted that there are “undertaker bees” that remove dead bees from the nest. I’ve seen them do this. In the lab where I did my graduate studies, we had colonies of bumble bees which we placed in wooden boxes with a clear plastic top so we could see inside. These boxes were connected to a wooden, glass-topped tunnel that led to a screened flight cage–sort of like a gazebo where the bees could fly around. One day I saw a worker bumble bee carry a dead bee in her mandibles (mouthparts). She carried the dead bee through the nest, down the tunnel, and then dropped it inside the flight cage! An undertaker bee in action.
It makes sense that bumble bees would get rid of dead bees in their nest. Corpses take up precious space in a busy home, they could carry disease or parasites, and in my experience, dead bumble bees stink! Bumble bees like to keep a clean, healthy nest (for instance, they do all their pooping outside), and dead bees would be something they would want to get rid of.
After I tweeted my bee fact, I wondered: What, if anything, do we know about these undertaker bees? Has anyone done any research?
I came across a study that was published last year by a team of scientists from the United States and New Zealand. They focused on the species Bombus impatiens, the common eastern bumble bee, which is found across most of North America. I also worked with the common eastern bumble bee for my own research.
The idea behind the scientists’ experiment was simple: place dead bees into bumble bee nests and see what the bees do. The scientists mounted a video camera above each nest box so they could record the behaviour of the bees.
The scientists had three colonies of bumble bees, all in their own nest boxes. To tell each bee apart, they labelled each worker bee by gluing a numbered plastic disc to their thorax (the middle part of their body). Where did they get the dead bees? They plucked some of the worker bees from the colonies and froze them. Poor bees! But it was the most humane way to sacrifice them while still keeping them intact.
Coloured, numbered discs were glued to the thorax of the dead bees, too, although a different colour was used from the live bees. Then, every so often the scientists placed five dead bees into each of the three nests. If a bee pulled on a dead bee with her mandibles, she was considered an “undertaker” and her “tug time” (the amount of time she spent tugging on the corpse) was recorded. A corpse was considered to be removed from the nest when it was tugged past the threshold of the nest entrance.
When there were no corpses in the nest, the scientists watched and classified other behaviours. “Nursing” was when bees fed larvae (baby bees), kept the baby bees warm, made honeypots out of wax, and inspected the larvae and honey pots. “Guarding” was when bees perched near the entrance of the nest, fanned their wings (to keep the nest temperature steady), or patrolled the nest. “Foraging” involved going outside the nest to collect food (pollen and/or nectar). Bees who sat still in the nest and seemed to do nothing were labelled, “inactive.”
So, what did the scientists find? About a third of the bees in a nest participated in corpse-tugging at some point. “Guard bees” tended to spend more time tugging corpses compared to the other tasks of nursing, foraging, or being inactive. These more consistent corpse-tugging “undertaker” bees tended to be bigger than other bees, and the bigger bees tended to be more successful in fully removing dead bees from the nest. Interestingly, on more than one occasion, one bee was seen dragging a corpse to the back of the nest, away from the entrance, digging a hole, and placing the dead bee inside the hole. Why did she do this, instead of taking the dead body outside the nest? The scientists don’t say in their report whether these corpses were left buried or whether they were eventually dumped outside the nest. Still, pretty peculiar that only one bee did this.
The team of scientists point out that it makes sense that guard bees would act as undertaker bees. Guards might be more likely to notice changes inside the nest, such as the presence of a dead body. Dead bee bodies probably give off chemical cues, such as a distinctive smell, that the bees can detect. So maybe there aren’t really “undertaker bees” after all, but instead, corpse disposal is just one task of guard bees.
Walton, A., Jandt, J. M., & Dornhaus, A. (2019). Guard bees are more likely to act as undertakers: Variation in corpse removal in the bumble bee Bombus impatiens. Insectes Sociaux, 66, 533-541. https://doi.org/10.1007/s00040-019-00718-8
I recently discovered even more evidence that bumble bees are awesome.
A team of scientists in Switzerland and France saw bumble bees biting holes in the leaves of some black mustard, eggplant, and silverleaf nightshade plants. No one had ever reported bumble bees biting leaves before. From what the scientists could see, the bees were not eating the leaves. They were also not bringing pieces of leaves back to their nest. So why the heck were they biting them?
The scientists knew that when some plants experience stress they tend to grow flowers. The plants that the bumble bees were biting did not have any flowers yet. Were the bees trying to speed up the plants’ flowering process?
Also, the scientists suspected that the bumble bees were after pollen. The bees were starting new colonies, and larvae (baby bees) need pollen as a protein source to grow. The bees might have been saying to the flowers, “Hurry up and flower! We need some pollen!”
This was a perfect circumstance for an experiment! And they way the scientists investigated this leaf-biting behaviour was very clever. They used laboratory and field experiments.
First, the laboratory experiments. The scientists let buff-tailed bumble bees (Bombus terrestris, widely found in Europe) fly around tomato and black mustard plants that only had leaves but no flowers. After the bumble bees had bitten 5 to 10 holes in the plants’ leaves, the scientists removed the plants. Then they did something really smart: They paired each bee-damaged plant with a plant that they had damaged themselves using forceps and a razor, to copy as closely as possible the way the bees had bitten the leaves. The result? The bee-damaged plants sprouted flowers up to 30 days earlier than normal, undamaged plants or plants that were damaged by the scientists. By biting the leaves, the bumble bees were speeding up the plants’ flowering process! Amazing!
For the next laboratory experiment, they gave some colonies of bumble bees lots of pollen in their nest, whereas for other colonies they gave none: the bees had to go out and get it themselves. The scientists then let bees from both types of colonies (pollen-rich or pollen-deprived) fly around young black mustard plants that had no flowers yet. They found that bees from pollen-deprived colonies bit holes in the plants’ leaves way more often than the bees from pollen-rich colonies. This is a convincing sign that the bees were biting the leaves in order to “tell” the plants that they needed pollen.
And finally, the field experiment. The scientists wanted to make sure that this leaf-biting behaviour happens in natural environments and not just in laboratories. So, they put some young colonies of bumble bees on the rooftop of a university building, along with some plants that had not flowered yet. They did this from March to May. This timing was important. Their bees were free to fly wherever they wanted to get food, but in March there wouldn’t be any flowers anywhere yet. But come May, there would be plenty of flowers to be found beyond the rooftop garden. Sure enough, the scientists discovered that the bees damaged many more plants in the early part of spring when no flowers could be found, but that damage decreased as spring progressed and flowers started to appear elsewhere.
The field experiment was also run between June and July, when plants are in full bloom. The scientists offered their rooftop colonies of bees some plants that had not yet flowered. The result? There was way less leaf damage to the flowerless plants they had placed near the colonies, presumably because the bees were flying farther to get pollen elsewhere. But the really cool part? They saw different species wild bumble bees biting holes in the leaves, too–not just bees from their own colonies! Wild bees, then, bite leaves as well.
What I think is so cool about all of this is that bumble bees have somehow figured out a way to make plants bloom faster when they are just establishing their families and are in need of pollen. This could be an adaptation to cope with climate change: cooler springs make it less likely that flowers will bloom on time, so bees help them speed up. And what’s even extra cool is that it is not just leaf damage alone that causes the flowers to come out early: something about bee bites in particular makes the plants sprout flowers. Are they injecting some kind of chemical into the plant? Do bumble bees have magic spit?
Sigh…bumble bees are amazing.
Pashalidou, F. G., Lambert, H., Peybernes, T., Mescher, M. C., & De Moraes, C. M. (2020). Bumble bees damage plant leaves and accelerate flower production when pollen is scarce. Science, 368, 881-884. DOI: 10.1126/science.aay0496
Chittka, L. (2020). The secret lives of bees as horticulturists? Pollen-starved bumble bees may manipulate plants to fast-forward flowering. Science, 368, 824-825. DOI: 10.1126/science.abc2451
May 20th is World Bee Day! I found a really cool research article that features both honey bees and bumble bees, and I thought I’d share it to help celebrate.
By far, honey bees are the more well-known of the pollinators. These are the bees that beekeepers take care of in tall, wooden hives in a field or in their backyard. Commercial beekeepers rent their honey bee hives to farmers to pollinate food crops, as opposed to hobby beekeepers, who just let their beehives stay put and harvest honey every once in a while. Although commercial beekeepers collect and sell honey, too.
The reason why wooden honey bee hives are so tall is because there are thousands of honey bees in a honey bee colony. They need lots of room to move around, raise baby bees into adults, and store their honey. Honey bees are used to pollinate food crops because there are many bee mouths to feed, so lots of honey bees in a hive go out to collect nectar (which the adult bees drink for energy) and pollen (which has the protein needed by baby bees to grow).
What is pollination, anyway? Pollination happens when pollen grains are moved from one part of the flower to another. When this happens, the flower can turn into fruit and create seeds, and the seeds allow new plants to grow. When a honey bee visits a flower, pollen grains stick to her, and as she moves around they can rub off onto the part of the flower that receives pollen. So in a way, bees pollinate flowers by accident!
But honey bees are not the only pollinators. Flies, butterflies, bats, hummingbirds, beetles, and moths also pollinate flowers. Some plants are even pollinated by the wind! But there are also thousands of other species of bees besides honey bees that are pollinators. One type of bee that pollinates flowers happens to be my favourite type of bee: the bumble bee!
Why are bumble bees my favourite? Besides looking like little winged teddy bears, they are quite tough little workers. Thanks to their fuzzy coats, they can go out and forage (collect food) when it is cooler outside, and because of their bigger size they can withstand stronger winds compared to honey bees. I remember doing some research in a blueberry field and the weather turned rather chilly and windy…a storm was coming. When I looked around, all of the honey bees had hurried on home but bumble bees were still out in force, collecting food, until the first few drops of rain arrived.
If bumble bees are such good little workers, why don’t farmers use them to pollinate their crops? Well, some do. There are companies that breed bumble bees and sell them to farmers, particularly to pollinate greenhouse tomatoes (honey bees don’t pollinate tomatoes). However, the colonies of bumble bees that come from these companies often have disease, due to the factory-like conditions that they are bred in. But that’s a story for another day. (I talk more about this in my upcoming book, The Beekeepers, to be released in March 2021.) But bumble bee colonies are quite small compared to honey bee colonies: a family of bumble bees is usually around 100-200 worker bees, plus the queen. Because there are so fewer mouths to feed, only a handful of bumble bees go out to forage at any one time. So a LOT of bumble bee colonies are needed to pollinate the vast fields of food crops that exist today. And, quite simply, people have used honey bees for hundreds of years to pollinate crops, whether or not there exist better native animals out there that can do a better job.
ANYWAY…all of this is to say that even though people use honey bees to pollinate their crops, there exist multitudes of native, wild critters, such as bumble bees, that pollinate the crops, too. Like in the blueberry field I was in: the farmer was using honey bee hives, yet bumble bees that naturally lived in the area were taking advantage of the bounty, too. (Honey bees are not native to North America. They were imported from Europe hundreds of years ago.)
Which brings me to the research study: could naturally-occurring bumble bees actually help honey bees do a better job at pollinating plants?
With some crops such as sunflowers and almonds, there is evidence that when in the presence of bumble bees, honey bees performed better. Specifically, they were more likely to fly to different rows of plants rather than sticking to just one plant or plants that were close together. Flying between distant plants causes what is called cross-pollination: taking pollen from one plant and delivering it to one that is further away tends to result in better fruit. A group of scientists in Belgium decided to study this systematically in sweet cherry orchards, to see if bumble bees do in fact influence honey bees to do a better job.
The scientists chose eight sweet cherry orchards across Belgium that were in full bloom. They made sure that each orchard was surrounded by hedgerows, wildflowers, trees, forests, and/or shrubs so that there would definitely be wild bumble bees living nearby.
In each orchard they selected blocks that were each roughly 4 metres by 5 metres. In 25-minute intervals, the scientists used a net to catch every honey bee and bumble bee that visited the cherry blossoms. They then put each bee in a tube so they could identify it, and also so that they didn’t count the same bee twice. When 25 minutes were up, they released the bees. This data allowed them to measure bumble bee abundance, which was the number of bumble bees they counted, and bumble bee richness, which was the number of different species of bumble bees they caught. They also measured honey bee abundance (the number of honey bees they caught).
At the same time as bees were being caught and identified, other scientists walked slowly up and down the rows of cherry trees. When they saw a bee visit a cherry blossom, they noted whether it was a honey bee or a bumble bee, and they followed it to see whether its next visit was to a tree in the same row or to a tree in a different row. If a bee visited trees in different rows, this meant that the cherry blossoms were being cross-pollinated, and this should result in better cherries (bigger, juicier, and overall higher quality).
What did the scientists find? It was clear that bumble bees were the superstars! Compared to honey bees, bumble bees visited around twice as many cherry blossoms and changed rows almost twice as often. But the really cool thing? When there were more bumble bees and more types of bumblebees around (that is, high bumble bee abundance and richness), the better the honey bees performed! The honey bees visited more blossoms and changed rows more often when in the presence of bumble bees. Somehow, bumble bees influenced honey bees in a positive way to get more cherry blossoms pollinated.
So, what this research tells us is that it is important to provide places for wild bumble bees to live around food crops, even if the farmers are using honey bees to pollinate their plants. Providing habitat for bumble bees is a win-win situation: the bumble bees can have a home, influencing honeybees to do their best, and in the end, we can harvest better quality food.
But how exactly did the bumble bees influence the honey bees? Were they somehow yelling at the honey bees, “C’mon, sisters! Step it up!” Were they somehow showing the honey bees how to do a better job? That’s another puzzle for another research study!
What Can You Do to Help the Bees?
This post on World Bee Day would not be complete without some tips about what you can do to help bees. Here are some suggestions:
DON’T START KEEPING HONEY BEES! Many people think that by getting a honey bee colony and keeping it in their backyard, they are somehow “helping the bees.” Sorry, but no, you are not. Honey bees are not native to North America, and they take food and space away from native bees, like bumble bees, who are trying to live in the wild. Honey bees can also introduce diseases into the wild, and can make native critters (like bumble bees) sick.
AVOID PESTICIDES. There are tons of research studies that show that pesticides harm and even kill bumble bees, honey bees, and other insects. A well-manicured lawn is a wasteland for bees and other critters anyway.
TRY THE “MESSY LOOK.” Let your yard, or parts of your yard, go wild and see what happens. Many wildflowers and weeds are actually quite pretty. And many wildflowers and weeds provide nectar and pollen for bees. Leaving piles of leaves and branches in your yard also provides a place for the bees to hibernate for the winter or escape bad weather.
TRY TO PLANT NATIVE FLOWERS. Wild bumble bees know best the types of plants that naturally grow in their area. So why not do a bit of research and find out what plants naturally grow where you live? The bees will thank you!
Eeraerts, M., Smagghe, G., & Meeus, I. (2020). Bumble bee abundance and richness improves honey bee pollination behaviour in sweet cherry. Basic and Applied Ecology, 43, 27-33. https://doi.org/10.1016/j.baae.2019.11.004