The Pollen Landscape

Joss Bartlet

• Éditeur: Northern Bee Books
• Année: 2021
• ISBN:
  9781912271924
• Sujet: Tecnologia e ingegneria
• Sous-sujet: Agricoltura

In this book, we are going to follow one colony of bees through their year of gathering pollen, to see what they find, and how they use it. We will look at the plants which make the pollen too, and the different aspects of the relationship that pollen creates between flower and bee.With the help of a microscope, we can examine something of the variety of pollen forms, and see how those can affect the bees as they collect them. The cycle of the hive is obviously bound to the seasons, because these help to determine what food they can find, but to the landscape as well, and the kinds of plants it provides.So we will look at where the bees of this north Wales hive find their pollen, and use that to consider how they cope, or struggle to cope, in the landscapes that they share with us, and that we alter and shape for our own needs. Altogether, as well as seeing the variety of pollen types gathered by a particular colony in a particular place, we are going to examine the whole relationship between honey bees and this part of their diet that they work so hard to find.

1. Honey bees and pollen

My grandfather kept bees, in a couple of hives on the road verge behind his house. Like many beekeepers, he had his own ways: he believed, for example, that stings became less painful the more you had, and would put his hand into the hive in spring to get the first ones over with. Presumably the immunity faded over winter, because he had to repeat the process every year. And though most beekeepers concentrate on honey, and he won prizes for his in the village show, he lost interest in that and turned instead to making mead. I never tasted it, but I remember when he bottled it a scent so heavy it seemed to sink, and the colour when he opened it, like pouring yellow light into the glass.

Mead today is one of the less usual products of the hive, but in making it my grandfather was maintaining an ancient connection between people and bees. The Anglo-Saxons gathered in their meduærn, or mead hall, and in the early Welsh poem, the Gododdin, where the warriors feast for a year in preparation for battle, what they drink is ‘medd’. The poem might be almost fifteen hundred years old, but the drink is certainly much older than that, as the similarity in the Welsh and English words may show. Sometimes languages have similar words because they inherit them from a parent tongue, and this is what has happened here. Words related to ‘medd’, like ‘med’ in Czech, and ‘mádhu’ in Sanskrit, occur in languages across Europe and south Asia, suggesting that the idea of a drink made from honey was already being expressed in the ancestral language from which all those tongues derive. Something like mead must have been enjoyed thousands of years ago.

The same is true of the honey from which mead is made. Related words can show a long history again: mêl in Welsh and meli in Greek, for example. And this time there is other evidence too - rock paintings in eastern Spain, dated to about 7000 BCE, show a human figure using a ladder to reach a nest, while bees fly around their head. In a world before cheap sugar, we can imagine risking stings for the sweetness in a comb of honey. Still, surely they would hesitate, and watch the bees for a while before they dared to rob them. And when they did so, these honey-gatherers must have noticed something much more obvious than the nectar from which honey is made: the balls of pollen that many of the bees would have carried on their legs.

Figure 1: pollen loads brought to the hive. The orange pellets are from dandelions, yellow from willow, white from wood anemones.

Perhaps they wondered about these coloured loads, or perhaps someone high up a ladder with angry bees around their head has other things on their mind. We don’t know, because unlike honey, or the mead we can make from it, pollen has no everyday use to make it worth recording. There is no pollen in poetry, no paintings on walls, no reference to pollen loads at all until Aristotle, only four centuries BCE. And even after that it takes another two millenia and the invention of the microscope before anyone is sure of what they are. But in recent years, pollen has moved closer to centre stage. The relationship between insects and flowering plants, which has evolved over millions of years, may not be too far from a catastrophic collapse. The numbers and diversity of pollinating insects are declining, and there has never been more research into what they do. Pollen is part of that: the COLOSS honey bee research network, which has members in almost a hundred countries, carried out surveys in 2014 and 2015 on pollen brought to hives across Europe. In the UK, the National Honey Monitoring Scheme uses the latest methods of genetic sequencing to identify the pollen grains which end up in honey samples, and from those the plants from whose nectar that honey is made. Pollen today is a gateway to a dynamic and fascinating field of research. But it also offers something else for anyone who keeps or watches bees. Unlike the nectar or water that bees collect, but carry hidden away inside their bodies, with pollen we can see what they are doing. Sometimes it can be an indicator of what is happening in the hive: pollen collection in spring is a sign to the beekeeper that the queen has survived the winter, and the colony is raising young. Or if the colony has to rear a new queen, then a beekeeper will watch for pollen coming in to suggest that they have succeeded, and the queen is laying eggs. And more broadly it tells us about the world of the bees outside the hive: we can see from the pollen which plants they are visiting, and sometimes from that we can have an idea of where they have been. We can see how these things change with the seasons and from year to year, and with that, like anyone who finds a reason to stop and look, find ourselves connected more closely to the natural world.

Depending on the weather, the pollen year for the British honey bee can extend from the first pellets of hazel in January or February to the last loads of willow in October, a rhythm almost a full year long that can be followed with the pollen that they collect. The length of the season is a tribute to the adaptability of the honey bee. Bees which live in social groups, like the honey bee, probably evolved in a tropical zone and enjoyed a climate very different from the temperate regions where so many are kept now. ‘It may be said that in our country,’ grumbled R.O.B. Manley, a notable authority between the wars, ’ the weather in summer-time is as a general rule about as bad as it can well be, considered from the point of view of the beekeeper’. Even so, the ability to store enough food to see them through winter allowed the honey bee to spread far to the north after the last ice age, and now their lives are regulated by seasons quite different from those that their ancestors would have known. The pollen year becomes a way to follow that, and even in my garden in north Wales, it can begin before January ends. Depending on winter conditions, the catkins of hazel are often advanced enough by then to release a puff of yellow pollen at the touch of a finger, and bees will work them on a sunny day. But usually the cold weather then closes in again, the catkins turn brown and have little to offer, and the bees retreat to their hives. So the real start of the year, the time when the bees show the first signs of the frantic, no time to lose attitude that they will keep for the next seven or eight months, comes in the second or third week in February. By then, there are clumps of snowdrops in the garden and along the base of the hedge in front of the house. If it is sunny enough to tempt the bees out to the snowdrops, then it is sunny enough for crocus flowers to open too, and soon each of those will have two or three bees circling the cup of petals, some gathering the orange pollen into a ball to be carried back to the hive.

But this early in the year, days suitable for foraging are likely to be the exception, and the start of the year is an uncertain time. In 2019, the year we will follow here, the bees were active throughout February and March. But a year before that they were busy on February 18^th, and then a high pressure system settled over us, the wind blew from the north-east, and there was heavy snow. March remained cold and wet: I took one pollen sample on the 25^th, but that was the only time in the month. Six or seven weeks of pollen were missed. For honey bees this far or further north, this kind of uncertainty can make spring the most perilous time. The honey they made last year to see them through the winter, and the pollen they stored too, may be running low, and poor weather can stop them collecting more. Meanwhile, inside the hive, the new season is well under way. The queen is laying eggs, there are new generations of bees to be made. And making bees, as we shall see, is what pollen is for. Just as much as the honey that we immediately associate with bees, the future of the colony is bound up with the pollen they can collect.

In this book, we are going to follow one colony of bees through their year of gathering pollen, to see what they find, and how they use it. We will look at the plants which make the pollen too, and the different aspects of the relationship that pollen creates between flower and bee. With the help of a microscope, we can examine something of the variety of pollen forms, and see how those can affect the bees as they collect them. The cycle of the hive is obviously bound to the seasons, because these help to determine what food they can find, but to the landscape as well, and the kinds of plants it provides. So we will look at where the bees of this north Wales hive find their pollen, and use that to consider how they cope, or struggle to cope, in the landscapes that they share with us, and that we alter and shape for our own needs. Altogether, as well as seeing the variety of pollen types gathered by a particular colony in a particular place, we are going to examine the whole relationship between honey bees and this part of their diet that they work so hard to find.

Aristotle’s account of what we now call pollen loads is recorded in his History of the Animals. As well as honey, he wrote, ‘they have another kind of food, which is called cerinthus (bee bread) which is of an inferior quality, and sweet like figs. They carry this upon their legs’. This he noted almost two and half thousand years ago. The knowledge wasn’t lost: the Romans knew of ‘bee bread’ too, and every beekeeper since would have seen their bees bringing pollen loads to the hive, but investigating pollen isn’t easy. Without the means to study it (or the inclination either, perhaps, when it offers nothing like honey or mead) for two thousand years after Aristotle little more was learned. Given this long silence, the first thing to consider is how we began to find out more.

2. Looking at pollen. February 2019.

In 1945, beside a hive near Cardiff, Mary Percival recorded the pollen collected by a single colony of bees. She watched the bees at 8 a.m. for 35 minutes, and repeated this every hour until half past five. Between April and August that year, she recorded almost half a million of the pollen loads that the bees brought in, and identified them on the basis of their colour and texture alone.

Dr Percival chose her method because she believed that direct observation of the bees gave the most accurate results. It certainly lets you see every pollen pellet that arrives, but it is hard to think of a more difficult way. She had to pick out each pollen-bearing bee through what is often dense traffic at the entrance to the hive. Sometimes, she noted herself, they arrived in such numbers that they were inside before she could count them. And she had to distinguish between shades of colour that can differ hardly at all. It would be like standing on Oxford Street on a Saturday afternoon, trying to record the colours of the shoppers’ socks. And then giving the shoppers stings, and a suspicion of your plans. She did have one advantage, though: she was a university botanist with detailed knowledge of the flora around the hive. As part of her study, she spent one day a week examining the plants which grew within a half-mile radius of the hive, so that she had an idea of which kinds her bees might be able to find. So her choices for pollen identification would have been narrowed by knowing which plants were available at the time.

Not impossible, then, but even so the usual way of studying pollen is not to watch the bees directly but to use a pollen trap instead. Placed at the entrance to the hive so that the bees have to go through it on their way in, the trap is designed to part the pollen from the bee. Traps have drawbacks of their own, but as well as being easier than Percival’s approach, they give us the pollen to examine at leisure. Then, as we shall see, we can use features other than the colour of the loads to find out what they are.

There is a market for pollen, and so there are commercial designs of pollen trap, but most people make their own. This means that they can differ in their details, but the principle behind them is usually the same. When the trap is set, the bees returning to the hive have to push their way in through a mesh, with holes about 5mm across. The holes let the bees in – with a struggle – but as they push their way through, the pollen balls are sometimes stripped from their legs. The lumps of pollen then fall through a smaller mesh (too small for the bees to get through to retrieve their load) and into a collecting tray further down. The bees find themselves in the hive without their pollen, perhaps like when we go into a room and can’t remember what we wanted there.

Figure 2. Pollen trap

In this trap the collecting mesh is vertical. The trap is set by pushing the mesh into position, and a collecting tray is then left in a lower drawer. Other designs have horizontal mesh, with the trap at the bottom or the top of the hive, and some make the bees go through two layers of mesh instead of one, with the idea of making it more likely that the pollen will be caught. These kinds are often based on a design introduced by the Ontario Agricultural College in 1962, and look something like this one.

Figure 3: OAC type trap

One of the advantages of this kind is the drone escapes, fitted above the mesh. Drone bees are too big to fit through the pollen-stripping holes, and in their eagerness to leave the hive and look for a mate will either be crushed against the mesh, or maim themselves trying to get through. With the OAC design, they can find their way out through two larger exits and escape unharmed. Workers, of course, could also find their way back in through these and avoid the mesh, but the entrances are less obvious than the main opening, the bees are anxious to get in, and most go in through the trap.

No trap gets every load, which is a good thing: the bees need poll...