Notes from a Summer Cottage

by Nina Burton

  I had certainly noticed that the bumblebee queens were already waking up. After my encounter with the one who ended up in the rain gauge, I saw a number of bumblebees searching the property, surely on the hunt for a nesting site.

  They were drawn to rather varied areas. The dream house of a large earth bumblebee is an empty mouse nest with some leftover grass insulation, and if she finds such a spot she’s prepared to go to battle with any lingering mouse. A tree bumblebee, however, prefers higher locations, perhaps in the wall of an old building, with light insulation.

  Sure enough. As I cleared a few dried stalks of lemon balm at the corner of the cottage I heard buzzing nearby. Then, silence. After a few minutes it returned again, and a bumblebee popped up at the lower edge of the wall. She was a little reddish, just like the one I’d rescued from the rain gauge, so it could in fact have been the same individual.

  Might she remember me? Strangely enough, bumblebees can recognise humans. Or did the place seem vaguely familiar to her? Since it was a tree bumblebee, she could, in theory, have been born there the previous year. Now she crawled back in under the siding to stay for a while. This was just next to a bench where I was planning to sit down with my papers; during the warm half of the year I like to work outdoors. The light charges me like a solar cell as the insects buzz like a dynamo. If the bumblebee intended to make a home here at the corner of the cottage, we could keep quiet company together.

  Whatever the case, apparently she was going to live right next door to my family, so knowing something about my new neighbour felt reassuring. Now I was doubly grateful to the researchers who had investigated the activities of the bumblebee. The enthusiastic ecologist Dave Goulson had even equipped them with tiny transmitters that registered their flight, and, like others, he had also paid careful attention to what went on in their nests. Thanks to this, I had some idea of what life in that wall would look like during the coming spring.

  Unlike certain squirrels, a bumblebee doesn’t need much space. A handful of insulation will do. The only furnishings in her nest are a collection of small pots she prepares out of wax from a gland on her belly. Once they’ve been shaped by her jaws and front legs, she fills them one by one with the harvest from various flowers. One little pot is heaped with nectar – good to have on the days she can’t fly out. The others are stuffed with pollen and nectar kneaded into a dough, and on top of that she lays some of the many eggs she carries in her body. Once she’s inspected and covered the pots, she lies on top of them like an incubating bird.

  The fur on her abdomen is so thin that, like a bird’s brooding patch, it allows close contact with the eggs. They need to be kept at 30 degrees Celsius, and she has a good sense of temperature. If her fur isn’t enough, she can increase her body heat by vibrating her wing muscles. This raises her temperature when she flies, as well, so she is essentially warm-blooded.

  After a few days of brooding the larvae emerge from the eggs, and once they’ve eaten their fill of the pollen stored in the wax pots, they spin cocoons where they will spend a few weeks transforming into pale bumblebees. As soon as they’ve wiggled out of the cocoon shell, they crawl to the nectar pot to gather energy, and then they move close to their warm bumblebee mother to dry their limp wings. The first bumblebee children are few in number and quite small, since they still have minimal resources, but the mother needs to gain helpers quickly. From now on, she will focus entirely on laying eggs, so within a few weeks there might be hundreds of young bumblebees.

  I, too, had to plan to welcome a family, because even though we would be taking turns in the cottage, it had to have room for two generations. So the bunk beds were joined by a sofa bed assembled by a carpenter, and I myself dragged branches to the steep edges of the property to create low barriers. Hopefully this would deter the youngest from any spontaneous but perilous adventures.

  The baby bumblebees in the wall, however, would be completely unprotected once they left the nest. While they were allowed to stay inside it for a few days, caring for new pupae and guarding the entrance, they would later have no choice but to leave and gather food. This is an enormous task for a young bumblebee. Outside meant great tits who had learned to scrape bumblebee stingers off on branches, and there were few flowers to visit in the spring. In dry weather there might also be a shortage of nectar, and finding it in the first place was a saga unto itself.

  The first flight out begins with small circles around the nest area, for orientation purposes. All the distinctive features around it are carefully imprinted so the bumblebees can find their way home. Later, should something around the nest change, they are stumped. If, for example, you were to put a chair nearby they must perform another round of orientation flight to adjust their inner map, and if the chair is later removed they become confused all over again. I would really have to remember not to rearrange the furniture too much near that corner.

  In general, bumblebees seem to notice everything. They prefer to collect pollen from different kinds of flowers so the larvae in their nest receive a balanced diet, and that means finding their way to and from those flowers. Thanks to fine details, they can cover a large amount of territory. The thousands of facets in their eyes see the world from slightly different angles, working together to convey information about distance, speed and route as the bumblebee flies. At the same time, roads, waterways and fields provide landmarks for orientation. All the while, the antennae are attuned to Earth’s electromagnetic field and can react to minuscule changes in humidity, temperature and wind. What’s more, they log every scent and can tell if it is coming from the left or the right. When it’s time to make a precise landing on a flower, the antennae instead register the surface pattern of the petals.

  How can we see bumblebees merely as peaceful bon vivants? They’re efficient super-pilots with navigational instruments that don’t even exist in modern aircraft. Thanks to these instruments, they can hold a straight course at 25 kilometres per hour even in a stiff crosswind. They’re also the most industrious of all bees, making seven foraging trips per day and visiting four hundred flowers per trip. Since they fly even during the cool morning and evening hours, they often rack up eighteen hours of work in a day.

  Behind this efficiency are proven methods. They remember the locations of half a dozen habitats and recall at which times the flowers give the most nectar. Then they schedule their visits accordingly and move from favourite spot to favourite spot in a rational manner. Should someone else recently have visited a flower, they bypass it the instant they sense the traces. Each time they land, they follow the same routine. The nectar is sucked up into a special receptacle in their body even as the grains of pollen caught in their fur is combed towards the pollen sacks on their back legs. It’s important for the contents to be evenly balanced so they don’t fly in circles, as the loads they carry can almost equal their own body weight.

  Only when daylight begins to fade do they end their workday. Already when they left the nest in the morning, the three simple eyes on the tops of their heads had taken a reading of the position of the sun by gauging the intensity of its light, and the same happens again on the journey home. Then they know how much time has passed and which angle they should now take relative to the sun. A bumblebee has even reportedly found her way home from ten kilometres away, although her journey back took two days. At the same proportions, a human journey of that distance would be like taking a round trip to the moon.

  So, where does it come from, this strange claim that bumblebees actually couldn’t fly? Presumably it’s a result of comparing them to dragonflies or gliding aircraft. But bumblebee wings move more like the rotor of a helicopter or like rowing oars. When the edge of the forewing angles up in flight, it creates an air spiral that provides lift. The disadvantage is that wing speed almost matches the revolution speeds of a racing motorcycle, so it’s a technique that demands high amounts of energy. Some of the gathered nectar is usually consumed as fuel even durin
g the journey, and this means they need a lot of nectar.

  The flowers on the property made for excellent bumblebee resources, and they surely knew it. They love the blossoms of blueberry, lingonberry, heather, blackberry and raspberry; they love the flowers of old farm weeds and perennials, and herbs like wild mint and lemon balm – the very plant growing next to the tree bumblebees’ nest. And dandelions. The bumblebees enjoyed resting in those yellow blossom baskets with their sun-warmed nectar, and I liked to sit down beside them to listen to the hum of their wings.

  The bumblebee’s entire body can be a musical instrument. Wing muscles quake like guitar strings, and with each impulse the wing flaps twenty times. All in all, bumblebee wings beat two hundred times per second. When the buzz of their wings blends with vibrations from their back plates and the membranes of their respiratory openings, it sounds like singing.

  I noticed that it also took on a rhythm that described its very movement. The tones lowered as the bumblebee slowed down at a flower and paused briefly for nectar. Taking off required extra wingbeats, so the tone shifted again.

  It was fascinating to find that the business of life could create sound. Every insect has a frequency, from the bumblebee’s bass to the whining descant of a mosquito. The pitch is determined by the breathtaking wing speed. Wasp wings beat a hundred times per second; bees, two hundred; flies, three hundred; and mosquitoes, six hundred. Singer Gaby Stenberg made recordings of insect sounds and from them created a musical scale. A horsefly was C. A wasp – C sharp and D. A large bumblebee – D sharp and E. A bee – F. Another wasp – F sharp. A small bumblebee – G, G sharp and A. A flowerfly – B flat and B. A small bee – C. Altogether they formed a musical alphabet of wingbeats.

  The bumblebees could hear this wing music better than I could, even though they didn’t have ears. Again, they had hair to thank, or at least hair-like organs that captured even the tiniest vibration in the air. With their help, insects can perceive sounds at much higher frequencies than we do and can feel the air itself tremble with movement. Or, indeed, with longing. Female mosquitoes lure males with the tone of their wingbeats, so to be safe their wings are equipped with amplifiers. No wonder we can hear them on a summer night. At least to male mosquitos it is sweet music, and they immediately adjust their own wing sounds to the same frequency. For when a male is in tune with a female the two of them can mate.

  The sound of bumblebee wings soon began to feel like home, but I also heard the buzz of wings in more unexpected places. One day, after coming across some red paint in the workshop, I decided to freshen up the flaking south-facing side of the cottage. Just as I was about to start painting, a pair of bees appeared before me. I backed up a bit to see where they’d come from, and they approached the door as if they wanted in. Strange. But after a while I realised we had different entrances after all. They had made their home in the casing of the door.

  Aha, so multiple kinds of bees lived in the south wall. Was I on the verge of painting some sort of beehive? I had seen photographs of Slovenian beehives that had been painted like old farmhouse cupboards. The images were colourful in order to be visible through a swarm, and in a robust style often portraying beekeeping or a biblical garden of paradise. Such paintings could simultaneously demonstrate ownership and brag of a wealth of bees. But after all this was no beehive, for the inhabitants of the door casing were wild, solitary bees. They were called red mason bees, and, like the tree bumblebee, had a slightly reddish coat. Meaning all of them matched the colour of the house.

  The red mason bees must have been there since the summer before, when a lone female made her way into the wall to lay eggs in peace, just like the tree bumblebee. But from that point on she fulfilled her motherly duties in a different way. She left all her eggs in separate, small cells, each with its own stout supply of pollen, mostly from maples and oaks. Then she closed up the nursery and flew off. Even if she herself didn’t survive the winter, her children would make it through in the warm south-facing wall, and obviously they had. They’d waited like tiny commas as the months passed – and the tradesmen went back and forth through the door – slowly developing with the help of last year’s tree pollen. To me it seemed they gifted the house with a life of their own.

  They’re said to be a peaceful, even child-friendly species of bee, and solitary bees in general do tend to be less aggressive than those who have a common nest to protect. Perhaps some of the door-casing bees had already emerged when the pussy willow began to blossom, for they tend to coordinate in some mysterious way. The males would have been closest to the entrance so they could leave quickly. If there were to be new bees for next year, they had to mate as soon as possible. Still, they weren’t abrupt about it, because solitary bees can be highly attuned to the needs of others. The males would gently stroke the females’ antennae until they received a spirited ‘yes’, and afterwards they rested together for a long time. Later, perhaps, the door casing would become a nursery again, although no one in the house would notice the growing children before they flew the nest in the spring.

  In the bumblebee nest, however, a summer of busy family life awaited, right next door to the cottage’s combined bedroom and living room. To be sure, the bees would probably be quiet neighbours. Good-natured bumblebees are beloved by poets and children’s book authors alike, and their lives are characterised by a feminine sort of care. Brutal alpha males are largely absent from the insect world, where egg-heavy females are larger as a rule, and bumblebee nests are matriarchal to boot. They aren’t led by an old matriarch as elephants are, however, because a bumblebee mother is too busy laying more eggs. Instead, the daughters must take care of themselves and their younger siblings, and will do this in harmonious sisterhood until the end of summer. But the drama that then awaits them would make suitable subject matter for a Greek tragedian.

  In high summer, all would still be idyllic. Hot days are spent napping together, and if the temperature in the nest rises above 30 degrees Celsius a few individuals will post up near the entrance to fan in air with their wings. In the centre of them all, the bumblebee mother sits on her new eggs, fed by her sweet daughters.

  All along, time is slowly making changes to everyone’s hormones. The mother is aging, and the future demands more youthful forces. To comply with this urge, the daughters begin to give special care to a few eggs that will become new queens. But they must also be fertilised by a male.

  Up to this point, all the eggs have been fertilised by the sperm the queen stored after last year’s mating. With a chromosome from a drone, they become females, but without they become males. And now the queen begins to lay unfertilised eggs with a single chromosome. It’s immediately obvious that the bumblebees emerging from these eggs are different. The pattern of hair on their faces looks like a beard and mutton chops, and it’s also clear what they’re after. Outside the nest, they surround themselves with seductive scents, preferably that of lime blossoms, which can make bumblebees rather tipsy. They leave their delicious scents in long trails on bushes and trees.

  Sure enough, the newly born queens quickly fall for the lecherous males. In the considerate way of the bumblebee, they make sure not to sting their partner during the act of mating, and when their connected bodies plunge to the ground the queens are filled with new life. If this life is to have any chance of survival, they must store energy of their own before hibernation, so the queens never return to their siblings in the nest.

  Life is changing there as well. The flowers are giving less and less nectar, and there’s more and more tension between bumblebee mother and daughters. When the daughters realise she has laid unfertilised eggs, they begin to do the same, for the whole nest is under the influence of hormones. But their egg-laying makes the once benevolent bumblebee mother angry. Perhaps it’s because this little stunt goes against the principles of their society, or perhaps it’s because she is genetically closer to her sons than second-generation offspring. In any case, she
bites her egg-laying daughters and eats up their eggs. It doesn’t matter that those are her grandchildren. The daughters respond by ganging up on her and eating up her male eggs. It makes no difference that those are their brothers.

  Even though all of this is determined by biological patterns of action, it’s still a sad story in the end. By the time the ever balder and more fragile bumblebee mother tries to retreat from the skirmish, it’s too late. As in a classical tragedy, she is either killed and flayed by her daughters, or left to starve to death in her disintegrating nest.

  The only survivors are the fertilised young queens that have already left the nest. Certainly, some of them will also eventually starve or be eaten, if they don’t moulder in some damp hibernation spot. But some of them may yet wake up with the first flowers in spring.

  What drama can arise within a family. At least the solitary bees of the door casing avoided such a life. They had, on the whole, fewer opportunities for conflict, since their young had to fend for themselves. With no new generation or common nest to defend, they had never developed social behaviours.

  Yet, like bumblebees, solitary bees are actually better pollinators than honeybees, and since they have only themselves to rely on they can be quite clever. For instance, a solitary bee has been observed removing a nail from its intended nest all on its own. When solitary bees are brought together, they can also help each other out with difficult tasks. But if they are incorporated into a colony with divisions of labour, it seems that their broad repertoire shrinks, rather like when craftspeople become factory workers.

  So, life can function well in different constellations even among bees, for single life and family life each have their own set of advantages. But it’s the reclusive traits that are dominant. Out of the nearly three hundred species of bees found in Sweden, all are solitary except for the honeybee and about forty bumblebee species. And even bumblebee societies begin with a single queen, although her daughters later remain in the nest. Why is that? Why don’t they build their own small families, or choose an independent life as solitary bees?