A Sting in the Tale (8 page)

The earliest bees, 130 million years ago, were almost certainly solitary species, and the majority of present-day bee species remain so. Each female builds her own nest, usually in a small hole in the ground, or in a tree or wall. In the leafcutter bees, the nest is lined with neatly snipped semicircles of leaves, glued together with silk. Once the nest is complete, the female bee fills it with pollen mixed with nectar and lays one or more eggs. The life cycles are very variable, but usually the female does not care further for her offspring, simply sealing up the nest entrance and leaving them to eat their pollen and develop on their own. Most solitary bees in temperate climates have just one generation a year, so the offspring will sometimes spend eleven months developing in the nest before emerging as adults.

Solitary bee species tend to be small, dark or drably coloured, which is why people seldom notice them. Nonetheless many are quite common and often live in gardens, some even nesting in the old mortar between the bricks of our houses. Only rarely do the lives of these inconspicuous creatures impinge noticeably on our own, although they probably contribute substantially to pollination of many crops without us being aware of it (honeybees often get all the credit).

I was once involved in a rather strange and less welcome instance of a solitary bee impacting on humans. I received a call from aeronautical engineers who were investigating the cause of an instrument failure which had forced a military helicopter belonging to a certain well-known superpower – confidentiality agreements prevent me from revealing which one – to perform an emergency landing. A small but vital instrument which measures airspeed and controls the speed of rotation of the rear rotor had failed, and the British manufacturers of the instrument found themselves under suspicion of supplying dangerously defective components. Upon close examination, it transpired that the cause of the fault was a plug of a sticky yellow substance blocking a tiny but necessary hole in the instrument casing. Their investigations suggested that the substance might be pollen, which was when I was brought in. It was indeed pollen, identifiable as belonging to some species of legume, no doubt placed there by a small solitary bee which had adopted the hole as its nest while the aircraft was parked. When it returned from a foraging trip, the bee was presumably rather disappointed to find that its nest had vanished.

Let us return to our journey through time. To recap, bees first appeared perhaps 130 million years ago, and by 80 million years ago some had evolved a social lifestyle, for the earliest fossil is of a social stingless bee. Some 65 million years after the first bees appeared (and, coincidentally, 65 million years before the present), the earth went through a catastrophic change. Most scientists these days agree that a meteor struck the earth roughly where the Yucatan Peninsula now lies, causing tidal waves and massive volcanic eruptions which filled the air with so much dust that it blocked out the sunlight, in turn causing temperatures to fall below freezing for months or years on end. Almost all large forms of life on earth then died out very swiftly, the dinosaurs among them. Amazingly, representatives of many of the smaller groups of organisms survived somehow. So far as the sparse fossil record reveals, the main insect groups – bees, ants, grasshoppers, beetles and so on – seem to have recovered swiftly, although it is likely that countless individual insect species became extinct. The flowering plants also survived, presumably as dormant seeds. Our own ancestors – small, furry and warm-blooded – may have kept themselves alive by feeding on the corpses of larger animals or on stores of seeds and nuts, and perhaps by keeping warm in the vast drifts of rotting vegetation that resulted from the forests' death. Before long the earth was once again teeming with life, albeit with rather smaller forms.

Our mammalian ancestors took advantage of the many unoccupied niches and diversified. Were it not for the meteor, it is doubtful if most of the larger mammals – including ourselves – would ever have appeared. Some species grew much larger, filling the roles once occupied by dinosaurs; these included ground sloths that stood 6 metres tall and weighed 3 tonnes, and the vast rhinoceros-like
Uintatherium
. It was into this world of giants that the first bumblebees appeared, about 30 to 40 million years ago. This corresponded with a period of cooler temperatures, which may have encouraged bees to become larger and furrier. Our best guess is that the first bumblebee lived somewhere in the mountains of central Asia, since this is still the area of greatest bumblebee diversity. From here they spread west, east and north from the Himalayas to occupy Europe, China and Siberia, and even up into the Arctic Circle. As bumblebees overheat in warm climates, they did not spread far southwards towards the equator, which is why until some recent deliberate introductions there were no bumblebees in Australia, New Zealand or Africa south of the Sahara. About 20 million years ago bumblebees crossed from Siberia to North America, where they thrived and spread southwards. Eventually about 4 million years ago a handful of species moved down through the mountain chains of Central America to occupy South America, becoming the only naturally occurring bumblebees in the southern hemisphere.

So now we arrive at the present day. The world is blessed with an extraordinary diversity of species of organism. About 1.4 million have been named so far, but estimates as to the true total vary hugely from 2 million to 100 million. Two hundred and fifty of the known species are bumblebees (members of the genus
Bombus
, of which twenty-seven occur naturally in the UK). There may be a few more yet to be found in remote regions, but probably not many. There are about 25,000 known species of bee (superfamily
Apoidea
, with 253 known from the UK), but many more undoubtedly remain to be discovered, particularly in the tropical regions. Bees in turn belong to the immensely successful insect order the Hymenoptera, which also includes ants and the wasps from which bees evolved, of which there are 115,000 known species. The Hymenoptera in turn are just one of many types of insect, collectively the most successful group of organisms on earth, with about 1 million named species, or about 70 per cent of all known species on earth.

Until recently, this number of species was the highest it had ever been since life began. However, in the last few thousand years it has started to drop rapidly as man has remoulded the surface of the planet. As our ancestors spread out from Africa, many of the large mammals such as mammoths, giant sloths and sabre-toothed tigers swiftly disappeared, either hunted to extinction by man or driven to extinction because their prey disappeared. Most would have had no defence against groups of men hunting with spears and bows and arrows. At present, species are going extinct at somewhere between 100 and 1,000 times the natural rate, largely driven by habitat destruction and the ravages wrought by invasive species. It is estimated that one species goes extinct every twenty minutes.

So far, only three bumblebees are thought to have gone extinct globally:
Bombus rubriventris
,
Bombus melanopoda
and
Bombus franklini
, but surely more will follow. It is the threat of extinction of large mammals such as tigers or rhinoceros that tends to capture the public's attention, but arguably it is the loss of the smaller creatures that should give us most concern. Insects are responsible for delivering numerous ‘ecosystem services' such as pollination and decomposition, and there is no doubt that little life on earth (including ourselves) could survive without them. As the famous biologist E. O. Wilson said, ‘If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos.'

CHAPTER FIVE

Finding the Way Home

Pigeons are not everyone's favourite creature. I must admit that I'm not enormously fond of the pestilential flocks of feral pigeons that infest many city centres, or even of the plump glossy wood pigeons that decimate my vegetable seedlings. Pigeons don't look particularly bright – in fact I've always felt that they have a rather vacant expression, and they do an awful lot of mindless cooing – but nonetheless they are capable of truly amazing feats of navigation.

Imagine this for a moment: you are locked in a dark box, transported for hours over 200 miles from home in a random, unknown direction, and then asked to find your own way back. You'd be rather annoyed and have no idea which way to go. You would of course ring the police, or ask someone for directions, but suppose you were unable to do either? Would you ever get home? Contrast this with the pigeon's response. With barely a moment's hesitation, the pigeon sets off flying at a brisk pace in precisely the correct direction. A few hours later it is happily perched in its loft tucking into a tasty bowl of grain. How on earth does it do this? Despite our vastly superior intellect and many years of scientific research, we have still not fully understood how pigeons navigate home so expertly from places that they have never previously visited. They can certainly use the sun or the stars as a compass, and can even tell where the sun is on heavily overcast days by their ability to detect the plane of polarised light penetrating the clouds. There is also some evidence that they have miniature magnets in their brains that enable them to detect the earth's magnetic field, so they have at least three inbuilt compasses. Impressive though all this is, you need more than a compass or three to find your way home if you have no idea which direction home is. And therein lies the mystery. It is almost as if they have a seventh sense (the sixth being the ability to detect magnetic fields) that we have yet to discover – a miniature GPS system perhaps, which tells them exactly where they are in relation to home.

At university I once had to write an essay on homing in pigeons, and became intrigued. In my later life as a university lecturer in the late 1990s, I couldn't resist investigating the navigation abilities of bumblebees. My experiments were very simple, and followed the model used by pigeon fanciers the world over. I set up five buff-tailed bumblebee nests in boxes in my garden. At that stage I was living in Southampton, at almost the opposite end of the country from my current home in Scotland. We had there a very dilapidated, ivy-encrusted structure that might once have been described as a gazebo, in which I placed the row of nests on a bench seat. This I called my ‘bumblebee loft'. When I first opened the doors to the newly installed bumblebee nests, the bees poured out, eager to explore their new environment. The air filled with hovering, circling bees, but within a few minutes they had all disappeared off into the surrounding gardens where they happily began foraging, returning a little later with balls of pollen on their legs and full honey stomachs. Once the bees were experienced, which took some only an hour or two, their behaviour on leaving the nest became obviously different; instead of indecisively hovering about or circling the nest, they whizzed out purposefully and disappeared at high speed.

When the bees had had a week to settle down, I began my homing trials. I caught them as they left their nest to forage and glued a tiny coloured and numbered disc to each of their backs so that I could recognise them again. I then placed them individually in small cylindrical cardboard pots (still known to entomologists as pillboxes, from their original use) and drove them in my car to a random location. At the time I had a rather silly two-seater Toyota MR2 sports car and the stack of cardboard pillboxes would sit on the seat next to me as I roared through the Hampshire countryside. At a random location, predetermined by blindly sticking a pin in a map, I would stop by the roadside and release a batch of ten bees, noting down their numbers. Invariably and understandably they looked rather confused, and would usually circle about in much the same way as they had when they first left their nest in my bumblebee loft. Some would head straight to the nearest flowers for a quick drink after the hot journey in the car. Within a few minutes, all had disappeared into the distance. At this point I would jump back into the car and race for home. Once back at the loft I would sit and wait for the bees to return, eagerly looking at each incoming bee to see if it was one of those I had released.

Some I released within 1 kilometre of my house, and more often than not these bees would beat me back to the nest. Even from 2 or 3 kilometres the bees would often be back within a few minutes, while I got caught up in the usual Southampton traffic (bees don't have to worry about such things). From further afield, it took rather longer. I released bees up to 15 kilometres from my house and sadly none of these ever returned. I like to think that they had a nice life, freed from the burden of work in the nest, and enjoyed themselves. Perhaps they found a different nest of their species and tried to lay some eggs in it (something that worker bees sometimes do). I am probably kidding myself. Whatever happened to them, I never saw them again.

The record distance over which a bee successfully returned to the nest was 10 kilometres. I was very proud of Blue 36. It took her two days to get home. Between 3 and 10 kilometres the number of bees that made it back steadily declined, and some would take up to three days to return to their nest. White 15 was released next to a nice patch of borage flowers in the grounds of Chilworth Manor, about 3 kilometres from my house. Borage produces particularly large amounts of sweet nectar, which both honeybees and bumblebees love (the flowers also make a colourful addition to salads, and the leaves are considered by some to be an effective cure for premenstrual tension, should you need any other reason to grow some). I happened to be doing some other experiments with bees on this patch of flowers, and was returning to them at regular intervals when not transporting bees around Hampshire or sitting by the loft waiting for them to return. White 15 was one of the clever bees that made her way home successfully and swiftly, but to my amazement on subsequent days she went back to the borage flowers. Every evening she was in her nest in my garden, but she would spend her days repeating the 6-kilometre round trip to Chilworth over and over again to collect nectar.