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1 Insect Anatomy
So how are they put together, these tiny creatures we share the planet with? The following section is a crash course in insect construction. It also shows that, despite their modest size, insects can count, teach, and recognize both one another and us.
What exactly is an insect? If you’re in any doubt, a good rule of thumb is to start by counting legs—because most insects have six legs, all attached to the midsection of their body.
The next step is to check whether the bug has wings. These are also on the midsection. Most insects have two pairs of wings: forewings and hind wings. You have now indirectly grasped one crucial hallmark of insects: their bodies are divided into three parts. As one of many representatives of the Euarthropoda phylum, insects are formed of many segments, although in their case, these have merged into three pretty clear and distinct sections: head, thorax, and abdomen.
The old segments still appear as indentations or marks on the surface of many insects, as if somebody had cut them with a sharp implement—and in fact, that is what gave this class of animals its name: the word insect comes from the Latin verb insecare, meaning “to cut into.”
The front segment, the head, isn’t so unlike our own: it has both a mouth and the most important sense organs—eyes and antennae. Though insects never have more than two antennae, their eyes can vary in number and type. And just so you know: insects don’t necessarily have eyes just on their head. One species of swallowtail butterflies has eyes on its penis! These help the male to position himself correctly during mating. The female also has eyes on her rear end, which she uses to check that she is laying her eggs in the right place.
If the head is the insects’ sensory center, the midsection—the thorax—is the transport center. This segment is dominated by the muscles needed to power the wings and legs. It is worth noting that, unlike those of all other animals that can fly or glide—birds, bats, flying squirrels, flying fish—insects’ wings are not repurposed arms or legs but separate motor devices that supplement the legs.
The abdomen, which is often the largest segment, is responsible for reproduction and also contains most of the insect’s gut system. Gut waste is excreted at the rear. Usually. The minute gall wasp larvae, which live out their larval existence in the gall a plant builds around them, are extremely well brought up. They know it’s wrong to foul your own nest, and since they are trapped in a one-room apartment without a toilet, they have no choice but to hold it in. Only after the larval stage is complete are the gut and the gut opening connected.
Insects are invertebrates—in other words, animals without a backbone, skeleton, or other bones. Their “skeleton” is on the outside: a hard yet light exoskeleton protects the soft interior against collision and other external stresses. The outermost surface is covered in a layer of wax, which offers protection against every insect’s greatest fear: dehydration. Despite their small size, insects have a large surface area relative to their tiny volume, meaning that they are at high risk of losing precious water molecules through evaporation, which would leave them as dead as dried fish. The wax layer is a crucial means of hanging on to every molecule of moisture.
The same material that forms the skeleton around the body also protects the legs and wings. The legs are strong, hollow tubes with a number of joints that enable the insect to run, jump, and do other fun things.
But there are a few disadvantages to having your skeleton on the outside. How are you supposed to grow and expand if you’re shut in like this? Imagine bread dough encased in medieval armor, expanding and rising until it has nowhere left to go. But insects have a solution: new armor, soft to start with, forms beneath the old. The old, rigid armor cracks open, and the insect jumps out of its skin as casually as we’d shrug off a shirt. Now it’s crucial that it literally inflate itself to make the new, soft armor as big as possible before it dries and hardens. Because once the new exoskeleton has hardened, the insect’s potential for growth is fixed until another molting paves the way for new opportunities.
If you think this sounds tiring, it may be a consolation to hear that (with a few exceptions) the lengthy molting process occurs only in insects’ early lives.
Insects come in two variants: those that change gradually through a series of moltings and those that undergo an abrupt change in the process of developing from child to adult. These transformations are called metamorphosis.
The first type—e.g., dragonflies, grasshoppers, cockroaches, and true bugs (the order Hemiptera)—gradually change in appearance as they grow, a bit like us humans, except that we don’t have to shed our entire skin in order to grow. For these insects, the childhood stage is known as the nymph stage. The nymph grows, casts off its exoskeleton a few times (just how many varies by species, but often three to eight times), and becomes increasingly like the adult version. Then, finally, the nymph molts one last time and crawls out of its used larval skin equipped with functioning wings and sex organs. Voilà! It has become an adult!
Other insects undergo a complete metamorphosis—an almost magical change in appearance from child to adult. In our human world, we have to turn to fairy tales and fantasy for examples of this sort of shape-shifting, such as kissed frogs turning into princes or Minerva McGonagall shape-shifting into a cat. But for insects, kissing and spells aren’t the cause of the change. The metamorphosis is driven by hormones and marks the transition from child to adult. First the egg hatches into a larva that looks nothing like the creature it will ultimately become. The larva often looks like a dull, pale, rectangular bag, with a mouth at one end and an anus at the other (although there are some exceptions, including many butterflies). The larva molts several times, growing bigger on each occasion but otherwise looking pretty much unchanged.
The magic happens in the pupal stage—a period of rest in which the insect undergoes the miraculous change from anonymous “bag creature” to an incredibly complicated, ingeniously constructed adult individual. Inside the pupal case, the whole insect is rebuilt, like a Lego model whose blocks are pulled apart and put back together again to make an entirely different shape. In the end, the pupa splits and out climbs “a beautiful butterfly”—as described in one of my all-time favorite children’s books, The Very Hungry Caterpillar. Total transformation is brilliant and undoubtedly the most successful variant. Most insect species on the planet, 85 percent of them, undergo this type of complete metamorphosis. This includes the dominant insect groups, such as beetles, wasps, butterflies, flies, and mosquitoes.
The ingenious part of it is that they can exploit two totally different diets and habitats as child and adult, concentrating on their central task in each phase of their lives. The earthbound larvae, whose focal point is energy storage, can be eating machines. Then, in the pupal stage, all the accumulated energy is melted down and reinvested in a totally new organism: a flying creature dedicated to reproduction.
The connection between larvae and adult insects has been known since ancient Egyptian times, but people didn’t understand what was happening. Some thought that the larva was a stray fetus that eventually came to its senses and crawled back into its egg—in the form of the pupa—in order to be born at last. Others claimed that two totally different individuals were involved, the first of which died and was then resurrected in a new form.
Only in the 1600s did Jan Swammerdam and his microscope demonstrate that the larva and the adult insect were the same individual throughout. The microscope enabled people to see that if a larva or pupa was carefully cut open, clearly recognizable elements of the grown insect could be found beneath the surface. Swammerdam enjoyed displaying his skills with scalpel and microscope before an audience and used to demonstrate how he could remove the skin from a big silkworm larva and reveal the wing structure beneath, complete with the characteristic veined patterning on the wings.
Even so, this did not become general knowledge until much, much later. In his journal, Charles Darwin noted that a German scientist was charged with heresy in Chile as late as the 1830s because he could transform larvae into butterflies. Experts still discuss the exact details of the metamorphosis process even now. Luckily, there are still some mysteries left in the world!
Insects don’t have lungs and don’t breathe through their mouths as we do. Instead, they breathe through holes in the sides of their bodies. The holes run, like drinking straws, from the surface of the insect into its interior, branching out along the way. Air fills the straws, and the oxygen then passes out of them and into the body’s cells. This means that the insects don’t need to use their blood to transport oxygen to the various nooks and crannies of their bodies. However, they do still need some kind of blood—known as hemolymph—to carry nutrition and hormones to the cells and to clear them of waste material. Since insect blood doesn’t transport oxygen, there is no need for the ferrous red substance that colors our mammal blood red. Consequently, insect blood is colorless, yellow, or green. That is why your car windshield doesn’t end up looking like a scene from a bad crime novel when you’re driving along on a hot, still summer afternoon but ends up covered in yellowish green splatters instead.
Insects don’t even have veins and arteries: instead, insect blood sloshes around freely among the bodily organs, down into the legs, and out into the wings. To ensure a bit of circulation, there is a heart of sorts: a long dorsal tube with muscles and openings on the side and at the front. Muscle contractions pump the blood forward from the rear, toward the head and brain.
Insects’ sensory impressions are processed in the brain. It is tremendously important for them to pick up signals from their surroundings in the forms of scent, sound, and sight if they are to find food, avoid enemies, and pick up mates. Although insects have the same basic senses as we do—they sense light, sound, and smell and can taste and feel—most of their sense organs are constructed in a totally different way. Let’s take a look at insects’ sensory apparatus.
The sense of smell is important for many insects, although they lack a nose, doing most of their smelling through their antennae instead. Some insects, including certain male butterflies, have large, feathery antennae that can pick up the scent of a female several miles away even in extremely low concentrations.
In many ways, insects speak through smell. Scent molecules allow them to send each other various kinds of messages, from soppy personal ads such as “Lonesome lady seeks handsome fella for good times” to ant restaurant recommendations: “Follow this scent trail to a delicious dollop of jam on the kitchen counter.”
Spruce bark beetles, for example, don’t need Snapchat or Messenger to tell each other where the party is. When they discover an ailing spruce tree, they shout about it in the language of scent. This enables them to gather together enough beetles to overpower a sickly living tree—which then ends its days as a kindergarten for thousands of beetle babies.
We miss out on most of these insect scents, which we simply can’t smell. But if you wander beneath the greenery of ancient trees on a late-summer day in the town of Tønsberg, southern Norway, you may be lucky enough to pick up the most delightful aroma of peaches: it is the scent of the hermit beetle, one of Europe’s largest and rarest beetles, wooing a girlfriend in the neighboring tree. The substance it uses rejoices in the thoroughly unromantic name of gamma-decalactone, and we humans produce it in labs for use in cosmetics and to add aroma to food and drinks.
The scent is very helpful to the hermit beetle, which is heavy and sluggish and seldom flies, or not far at any rate. It lives in ancient hollow trees, where its larvae gnaw on rotted wood debris, and it’s a real homebody: a Swedish study found that most adult hermit beetles were still living in the same tree they were born in. This lack of interest in travel complicates the business of finding new hollow trees to move into, and the situation is hardly helped by the fact that old, hollow trees are an unusual phenomenon in today’s intensively exploited forests and farmlands. As a result, the species, which is scattered across western Europe from southern Sweden to northern Spain (though not the British Isles), is decreasing all over its range and is protected in many European countries. In Norway, it is considered critically endangered and can be found in only one place: an old churchyard in Tønsberg. Or two places, to be precise, because some individuals have recently been moved to a nearby oak grove in an effort to secure the survival of the species.
Flowers have realized that scent is important to insects—or rather, millions of years of mutual evolution have resulted in the most incredible interactions. The world’s largest flower, which belongs to the Rafflesia genus and is found in Southeast Asia, is pollinated by blowflies. This means that “a scent of warm summer sun meets a cool evening breeze with a hint of amber and sensual vanilla”—to borrow perfume industry terminology—isn’t going to cut the mustard. No, indeed. If you want blowflies to come visiting, you need to yell at them in blowfly language. That is why the world’s biggest flower smells like a dead animal whose carcass has been lying around in the heat of the jungle a couple of days too many—a stench of rotting flesh that is irresistible if you happen to be a blowfly.
But you don’t have to go the jungle to find examples of flowers that speak the insects’ language of scent. The fly orchid is a protected native European species, rare in Norway and the United Kingdom but widespread throughout central Europe. It has strange brownish blue flowers that look just like the female of a certain digger wasp species. And its beautiful appearance is supplemented by the right scent: the flower smells identical to a female digger wasp on the prowl. So what is a bewildered newly hatched male digger wasp, whose short life is dominated by a single thought, to do? He falls for the trick and tries to mate with the flower. When things don’t go so well, he moves on to what he thinks is the next female and tries again. No luck there, either. What he doesn’t know is that during these ill-fated pairings, he has picked up some yellow structures that contain the fly orchid’s pollen, so the male digger wasp’s feverish flirting contributes to the flowers’ pollination.
And if you’re concerned about the fate of the unfortunate male, please don’t despair. The real females hatch a few days after the males, and then things really start heating up. In this way, the existence of both the fly orchid and the digger wasp is ensured.
Although communicating through scent is important for insects, especially if they’re searching for a mate, some rely on sound to find a partner instead. The grasshopper’s song is not designed to create the sound of summer for us humans but to find a girlfriend for the little green creature; it is usually the male calling out to the female, in the same way as male birds are frequently the keenest warblers. If you’ve heard the deafening wall of sound cicadas create in southern climes, bear in mind that it would be twice as loud if the ladies joined in. But as an ancient Greek saying has it, “Blessed are the cicadas, for they have voiceless wives.” Controversial as we may find this statement in modern society, let me just add that it may be pretty smart of the females to keep their lips zipped. Lovesick fellow cicadas aren’t the only ones attracted by the song. Scary parasites lie in wait listening, then sneak up to lay a tiny egg on the soloist. And although it might look quite innocent, it’s game over for the singer. The egg hatches into a hungry larva, which eats up the cicada from the inside out. Enough said.
Insects have ears in all sorts of peculiar places but rarely on their heads. They may be on their legs, their wings, their thorax, or their abdomen. Certain butterflies even have ears in their mouths! Insect ears come in a number of variants, and even though all of them are XXXS size, some of them are incredibly intricate. One type has a vibrating membrane, like a tiny drum, whose skin is set into motion every time sound waves from the air reach it. It isn’t unlike our own inner ear, just in a simplified miniature version.
Insects can also sense sound through different sensors connected to small hairs that pick up vibrations. Mosquitoes and fruit flies have these kinds of sensors on their antennae, while the bodies of butterfly larvae may be covered in sensory hairs, which they use to hear, touch, and taste. Some ears can pick up sounds a long way off, while others operate only over very short distances. It’s sometimes difficult to say what “hearing” actually is: for example, are you hearing or feeling when you pick up vibrations in the stem of the stalk of grass you’re perched on?
If you are small, you can use an amplifier to boost your sound—as do several species among the wood-boring beetles (Hadrobregmus pertinax and Xestobium rufovillosum). In the olden days, people thought that the sound they made was a forewarning of imminent death, but the actual explanation is much more prosaic. These beetles live out their larval existence in rotting woodwork, often in the timbers of houses. As adults, the beetles find partners by banging their heads against the wall. The sound transmits effectively through the woodwork and is picked up by both the beetles and us humans. This repetitive knocking is reminiscent of a ticking clock, or perhaps even more like somebody drumming his fingers impatiently on a table. According to ancient superstition, these sounds meant that somebody would soon die: they were a clock counting down the person’s final hours or the Grim Reaper waiting restlessly. It was probably just easier for people to hear the sounds at night in a quiet house, when, say, they were keeping watch at somebody’s deathbed.
There are other insect sounds that we hear distinctly even in the clear light of day, such as the cicadas’ song. Even so, cicadas aren’t the winners in the competition for the world’s noisiest insects. Adjusted for size, an aquatic insect a mere 2 millimeters long is the one most likely to walk away with the prize, because the male water boatman, part of the Micronectidae family, competes for the ladies’ attention by making music. But how are you supposed to serenade your sweetheart when you’re the size of coarsely ground pepper? Well, the little water boatman does it by playing himself, using his abdomen as a string and his penis as a bow.
Several years ago, a team of French scientists set up underwater microphones to record the song of male water boatmen—the first-ever bootleg recording of this serenade. And what a hit it was in its way: the scientists believed they could prove that these tiny creatures with their fiddling penises exceeded all bounds of reason when it came to sound production. An average sound level of no less than 79 decibels made by a critter a mere 2 millimeters in length: on land that’s equivalent to the sound of a freight train passing by at a distance of around 50 feet.
It seems almost beyond the realm of possibility, and it may actually not be true, either, because it’s a complicated business to compare sounds underwater and in the air. Perhaps the water boatman will turn out not to be the world’s noisiest insect after all. But the fact that it fiddles with its own penis—well, you can’t take that away from it.
Imagine if you could walk barefoot through the forest in the summertime and actually taste the blueberries in the bushes as you stepped on them! This is what houseflies do. They taste with their feet. And flies are unbelievably hypersensitive, apparently a hundred times as sensitive to sugar as we are with our tongues.
But there are a few disadvantages to being a fly, on top of being a mostly unwanted creature to begin with. Flies don’t have teeth or any other equipment that would enable them to eat solid food, which dooms them to an eternally liquid diet. So what is a poor housefly to do when it lands on something tasty, like your slice of bread? Well, it uses digestive enzymes from its belly to turn the food into a smoothie. To do so, it has to regurgitate some of its gastric juices onto the food, which isn’t so great for us because it means that bacteria from the fly’s last meal—possibly far from anything we’d classify as food—may end up on our slice of bread. But it’s great for the fly, which can now suck up the food. The housefly’s mouth is like a spongy vacuum cleaner head on a short shaft. The whole thing is attached to a kind of pump in the head, which creates suction, allowing the fly to vacuum up the yummy, nutritious soup.
Houseflies’ poor table manners and somewhat varied diet, which includes items such as animal dung, are the reasons they spread infection. The flies aren’t dangerous in themselves, but, like used syringes, they can carry infections and pass them on to us.
And now that I think about it, maybe it’s just as well we humans taste with our tongue and not our feet. Blueberry shrubs are one thing, but the thought of going around tasting the insides of your shoes all winter long is hardly appealing.
Insects’ senses are adapted to their environment and needs. Whereas dragonflies and flies need good vision, insects that live in caves may be totally blind. Insects that come into close contact with flowers, such as honeybees, can also see colors, but their color spectrum is shifted upward, so they don’t see red light. On the other hand, unlike us humans, they can see ultraviolet light. This means that many flowers we see as monotone, such as sunflowers, have distinctive patterns for a bee, often in the form of “landing strips” that direct them toward the source of nectar in the flower.
Insects’ compound eyes consist of many individual eyes. The brain merges all the tiny pictures together into a single large image, although it is coarser and fuzzier than the way we see the world. It looks a bit like a low-res photograph on your computer screen when you’ve zoomed in too close. There are plenty of reasons why insects don’t have driving licenses, of course, but sight is a big one: they would never be able to read a road sign at 60 feet, as the image would be too blurry.
That said, their vision is supremely adapted to the tasks that will fill their days. Take whirligig beetles, for example, shiny black pearls of beetles that dash around on the surface of the waters of our lakes. They have two pairs of eyes with different refractions: one pair for seeing clearly under water so that they can watch out for hungry perch, the other for seeing clearly above the water so that they can find food on the surface.
Insects can also see a property we humans are blind to: polarized light. This has to do with which plane the light is oscillating in, and it alters when sunlight is reflected—in the atmosphere or off a shining surface such as water. But let’s go easy on the physics and restrict ourselves to saying that insects use polarized light as a compass that enables them to orient themselves. We humans relate to polarized light only when we put on a pair of Polaroid sunglasses to reduce the glare of reflected light.
In addition to having compound eyes, insects may have separate simple eyes whose main function is to distinguish between light and dark. Next time you meet a stinging wasp, look it deep in the eyes and note how, in addition to the compound eyes on either side of its head, it has three simple eyes in a neat triangle on its forehead.
When it comes to having eyesight adapted to their daily business, dragonflies are in a class of their own: their vision is a major reason why these insects are deemed to be among the world’s most efficient predators.
Lions may put on an impressive display when they’re hunting in a pride, but they manage to chase down their prey only one in every four times. Even the great white shark, with its terrifying three-hundred-toothed grin, fails in half of all its attempted attacks. The dragonfly, however, excels as a lethal hunter, succeeding in more than 95 percent of its attempts.
Part of the reason dragonflies are such skilled hunters is their extraordinary command of the skies. Their four wings can move independently of one another, which is unusual in the insect world. Each wing is powered by several sets of muscles, which adjust frequency and direction. This enables a dragonfly to fly both backward and upside down and to switch from hovering motionless in the air to speeding off at a maximum of close to 30 miles an hour. No wonder the US army uses them as models when designing new drones.
But their vision also makes a significant contribution to their success. And perhaps it is hardly surprising that they have good eyesight when almost their entire head consists of eyes. In fact, each eye is made up of 30,000 small eyes, which can see both ultraviolet and polarized light as well as colors. And since the eyes are like balls, the dragonfly can see most of what is happening on all sides of its body.
Its brain is also prepped for supersight. When we humans see a rapid sequence of images, we see them in a flowing movement, a film, if there are more than around twenty images per second. However, a dragonfly can see up to three hundred separate images per second and interpret every one of them. In other words, a movie ticket would be wasted on a dragonfly. Where you and I see a moving film, it would simply see a very rapid slide show.
The dragonfly brain is also capable of focusing over time on one specific section of the enormous quantity of visual impressions being received. It has a kind of selective attention that is unknown among other insects. Imagine that you’re traveling across the sea in a boat and see another boat ahead of you, at a given angle to you. If you ensure that you always have the boat at exactly the same angle in your field of vision, you will end up meeting. In a somewhat similar way, the dragonfly brain can lock its attention on approaching prey, coordinating its speed and direction to ensure a strike—and yet another successful hunt. Intricate, well-designed sensory organs alone are not enough: you also need a brain that can process all the information as it streams in, seeking out relevant patterns and connections and sending the correct messages out again to different parts of the body. And even though insects have tiny brains, we will see that they are a lot smarter than we might assume.
Carl Linnaeus, the great Swedish biologist who classified our species, placed insects in a separate group, in part because he believed they didn’t have brains at all. Maybe that’s not such a surprise, because if you behead a fruit fly, it can live pretty much as normal for several days, flying, walking, and mating. Eventually, of course, it will starve to death, because having no mouth means not eating. The reason insects can survive in a headless state is that they have not only a main brain in their head but also a nerve cord that runs through their entire body, with “minibrains” in each joint. Consequently, many functions can be performed regardless of whether or not the head is in place.
Are insects intelligent? That depends on what you mean by intelligence. According to Mensa, intelligence is the “ability to acquire and analyze information.” Now, it’s unlikely that anybody’s going to argue that insects deserve to be Mensa members, but the fact is that they never cease to surprise us with their ability to learn and make judgments. Some things we believed to be the sole preserve of large vertebrates with proper brains also turn out to be within the capabilities of our tiny friends.
But not all insects are created equal, and there are great differences among them. Those with dull lives and simple habits are the least bright. You don’t need the wisdom of Solomon if you’re going to spend most of your life snugly tucked up in an animal hide with your sucking snout stuck in a vein. However, if you’re a honeybee, a wasp, or an ant, you’re more in need of intelligence. The cleverest insects are the ones that look for food in lots of different places and also form close bonds with one another; in other words, the ones that live alongside many others in a community. These critters must constantly be making judgments: Is that yellow thing over there a flower with sweet nectar, or is it a hungry crab spider? Will I be able to carry that conifer needle alone, or will it take several of us? Do I need to take a sip of this nectar to keep myself going, or should I take it home to Mom?
The social insects divide up jobs, share experiences, and “talk to each other” in an advanced way. This requires capacity for thought. To cite Charles Darwin: “The brain of an ant is one of the most marvelous atoms of matter in the world, perhaps more so than the brain of a man.” And that was without knowing what we now know: that ants are capable of teaching skills to other ants.
The ability to teach has long been seen as exclusive to us humans, almost a proof of an advanced society. Three quite specific criteria distinguish teaching from other communications: it must be an activity that happens only when a teacher meets an “ignorant” pupil; it must involve a cost for the teacher; and it must make the pupil learn more rapidly than it otherwise would have. The term is used for communication about concepts and strategies, so the honeybees’ dance (see page 22), which is more about process, is generally not viewed as teaching. However, it turns out that ants are capable of teaching things to other ants, through a process known as tandem running, in which an experienced ant shows the way to food. This occurs in a European species, Temnothorax albipennis, which relies on landmarks such as trees, stones, and other things, as well as scent trails, to remember the way from the anthill to a new source of food. In order for several ants to be able to find the food, a she-ant (all worker ants are female) who knows the way must teach it to the others. The teacher runs on ahead to show the way but constantly stops to wait for the pupil, who runs more slowly, apparently because she needs time to take note of the landmarks they are passing. When the pupil is ready again, she touches the teacher with her antennae and they continue on their journey. The behavior therefore satisfies the three criteria of genuine teaching: There’s a teacher and an “ignorant” pupil involved, the teacher must stop and wait, so there’s a cost, and the pupil must learn her way to the food more quickly than she would have on her own.
Bumblebees have also recently been inducted into the exclusive little group of animals that can teach tricks to their peers. Swedish and Australian scientists successfully trained bumblebees to pull on a string to gain access to nectar. They made artificial blue flowers in the form of plastic discs, which they filled with sugar water. When these were covered with a transparent plate of plexiglass, the only way of gaining access to the sugar water was to pull on a string attached to the fake flower. If the scientists let only untrained bumblebees loose on the covered flowers, they didn’t understand a thing. None of them pulled on the string—a great starting point. Then the bumblebees were given a chance to get acquainted with the “flowers,” to learn about the reward they offered. Gradually, the fake flowers were pushed farther and farther beneath the transparent plexiglass plate. This time, when the fake flowers were finally pushed fully beneath the plate, twenty-three out of forty bumblebees began to pull on the string. In this way, they drew the fake flowers out and were able to suck up the sugar water. Admittedly it was a long lesson: the whole business took a good five hours of training per bumblebee.
The next step was to see whether these trained bumblebees could teach others their peculiar trick. Three bumblebees were selected as “teachers.” New, untrained bumblebees were placed with them in a small transparent cage close to the flowers to watch and learn. Fifteen of the twenty-five “pupils” grasped the point by watching how their teacher did it and themselves managed to pull out their reward when they got to try afterward. All in all, this experiment showed both that the bumblebees could learn this rather unnatural skill and that they were capable of teaching the strategy to others.
Hans the Horse of Germany was a global celebrity in the early 1900s. He couldn’t just count, he could also calculate—or so people thought. The horse could add, subtract, multiply, and divide. He answered math problems by banging out the correct answer with his foreleg, and the horse’s owner, math teacher Wilhelm von Osten, was convinced that the animal was just as clever as he was. In the end, it turned out that Hans couldn’t calculate at all or even count. That said, he was a whiz at reading the minuscule signals in his questioner’s body language and facial expressions. The person setting the problem had to count, too, to make sure that Hans was giving the right answer, and a tiny, unconscious signal he made when the horse reached the correct number was all that Hans needed. In fact not even the psychologist who eventually unmasked Hans was able to control those signals.
However, bees actually can count—not very far, and they are no more capable of the four types of calculation than Hans was. Even so, it’s a pretty impressive feat for a creature with a brain the size of a sesame seed. To measure this ability, honeybees were placed in a tunnel and trained to expect a reward after passing a certain number of landmarks, regardless of how far they had to fly. It turned out that they could count up to four, and once they had learned to do that, they were able to count the landmarks even if they were a new type they had never seen before.
And bees aren’t just good at math (well, considering their size); they are also good at languages.
At around the same time as Osten and his not-so-clever horse were alive, a future Nobel Prize winner was growing up in the neighboring country of Austria. Even as a child Karl von Frisch loved animals, and his mother must have been extremely tolerant, since she put up with the abundant array of wild animals he brought home as pets. Over the course of his childhood, he noted 129 different pets in his journal, including 16 birds; 20-odd types of lizards, snakes, and frogs; and 27 different fish. Later, as a zoologist, he was especially interested in fish and their color vision. But almost by chance—largely because his aquatic research subjects displayed an unfortunate tendency to expire on the way to the conferences where he was supposed to be demonstrating his experiments—he switched to studying bees instead.
Frisch made two major discoveries: he proved that bees can see colors and that they can tell each other where to find food by performing a sophisticated dance. That was what won him a Nobel Prize in 1973. Frisch showed that when a honeybee finds a rich source of nectar, she returns home to the others and tells them where the flowers are. She dances in a kind of figure eight, waggling her rear and vibrating her wings in the parts of the dance when she is moving in a straight line. The speed of the dance communicates the distance to the flowers, while the direction she dances in, in relation to a vertical line, describes where the flowers are relative to the position of the sun.
Today, bees’ dance language is one of the best-researched and best-mapped examples of animal communication. But history could have turned out quite differently: in Adolf Hitler’s Germany, this research was nearly brought to a halt when it had barely begun. In the 1930s, when Frisch was working at the University of Munich, Hitler sympathizers scoured the university’s employee roster to root out Jewish workers. When Frisch’s maternal grandmother proved to have been Jewish, he was fired. But he was rescued by a tiny parasite—one that caused a disease in bees that was in the process of wiping out Germany’s bee population. Beekeepers and colleagues managed to persuade the Nazi leadership that Frisch’s future research was crucial if German beekeeping were to be rescued. The country was at war and in dire need of all and any foodstuffs farming could produce. A collapse of the honeybee population was unthinkable. Thus Frisch was able to carry on his research, for the good of both bee knowledge and Frisch’s career.
For a long time, we believed that only mammals and birds were capable of distinguishing among individuals, the very foundation of the capacity to develop personal relationships. This belief persisted until an inquiring scientist, with the help of some model airplane paints, began face painting wasps. The species concerned was Polistes fuscatus, an American member of the family of paper wasps. Paper wasps build nests from chewed-up wood fiber that look like a rosette of small larval cells. The nest hangs on a stalk, like an upside-down umbrella. Unlike regular stinging wasps, which also build nests from wood pulp, paper wasps’ nests do not have a protective envelope around the comb of larval cells.
This wasp lives in a strictly hierarchical society, where it’s crucial to know who’s the boss. Maybe that’s why they’re so good with faces. A wasp whose face had been painted in a way that altered her pattern of stripes met with an aggressive reception from her fellow inhabitants when she returned to the nest. They didn’t recognize her and were confused. As a control, the scientists also painted other wasps without altering their patterns of stripes. Those wasps did not experience any reactions on their return to the nest.
Another fascinating point is that after a few hours of jostling, the other inhabitants of the nest got used to the face-painted wasp’s new look. The aggression diminished, and everything went back to normal. The other wasps had learned that this was indeed the same old Waspella, despite her makeover. This implies that wasps actually have the capacity to recognize and distinguish among individual members of their community by their detailed facial cues or “features.”
Honeybees take the whole business up a few notches: they can distinguish among human faces in the form of photographic portraits. What’s more, they can remember a face they’ve become familiar with for at least two days. It is doubtful whether the bees relate to what they are seeing. They seem to believe the portraits they are presented with are really funny flowers, with the darker areas of eyes and mouth representing recognizable patterns on “petals” that are actually the outline of the portrayed face.
This is new and exciting information, which forces us to rethink how facial recognition works: after all, we’re saying that an animal whose brain is smaller than the letter o in this book is able to achieve similar things as we humans, with our cauliflower-sized brain boxes. Greater understanding of these processes may be able to help people who suffer from face blindness (prosopagnosia), which is the inability to recognize faces.
Perhaps this knowledge could be used in surveillance, at airports, say. Not by installing a glass cage of buzzing bees to scrutinize us sternly as we go through customs (although that would be pretty cool!) but rather by translating the principles that enable bees to recognize facial patterns into a logic that computers can follow. One hope is that this could lead to improved automatic facial recognition—of, say, wanted criminals—via surveillance cameras in crowded places.
In an attempt to organize the hordes of tiny creatures, we humans have split them into groups according to how closely related they are. It’s an ingenious system that starts with the kingdom, which is then divided into phylum and class, which are again divided into order, family, and genus before we come to species.
Take the common wasp, for example. It is a species that belongs to the animal kingdom, the Euarthropoda phylum, the Insecta class, the Hymenoptera order, the stinging wasp family, the Vespula genus, and, finally, the common wasp species.
All species have a two-part Latin name, which is written in italics. The first part tells you which genus the species belongs to, and the second part identifies the species. This system, introduced by Carl Linnaeus in the 1700s, makes it easier for biologists to be certain that they’re talking about the same species even when they’re communicating across national borders and language barriers. The common wasp, for example, has been given the name Vespula vulgaris. You can often grasp the meaning of the Latin names: for example, vulgaris means “common” (and is also the origin of the word vulgar).
Sometimes the Latin name tells us something about the insect’s appearance, as with the Stenurella nigra beetle, where nigra describes the color of this totally black species. Other times, the name has been borrowed from mythology, as in the case of the beautiful peacock butterfly, Aglais io. Io was one of Zeus’s mistresses, who also lent her name to one of Jupiter’s moons.
With hundreds of thousands of insects to name, entomologists sometimes go a bit wild, calling species after their favorite artists, such as the Scaptia beyonceae horsefly (see page 41) or characters from much-loved films, such as the Polemistus chewbacca, P. vaderi, and P. yoda wasps. Sometimes the species names contain a pun that you discover only when you say them out loud. Just try pronouncing the names of the bean-shaped beetle Gelae baen and Gelae fish or the parasitic wasps Heerz lukenatcha and its relative Heerz tooya!
There are around thirty different orders of insects in the world. Beetles, wasps, butterflies, flies, and true bugs are the five largest. Other orders include dragonflies, cockroaches, termites, orthoptera (grasshoppers and crickets), caddis flies, stone flies, mayflies, thrips, lice, and fleas.
Let’s start with beetles (coleoptera), one of the largest orders of insects worldwide, despite tough competition from the wasp order, where improved knowledge is leading to a steady rise in the number of species. The hallmark of beetles is that their forewings are hard, forming a protective shell over their back. Beyond that, beetles are incredibly varied in appearance and lifestyle and can be found on both land and water. There are more than 170 different beetle families, some of the largest being true weevils, scarab beetles, leaf beetles, ground beetles, rove beetles, longhorn beetles, and jewel beetles. All in all, there are around 380,000 known beetle species worldwide.
The wasp order (Hymenoptera) consists of familiar insects such as ants, bees, bumblebees, and stinging wasps, including many species that are social and live in colonies containing hordes of female workers and one or more queens. The order also encompasses many lesser-known sawflies and a huge number of parasitic wasp species. So far, we have identified more than 115,000 species in this order, but the number is rising steadily and this is probably the largest order of insects.
Butterflies and moths (of the Lepidoptera order) have wings covered in tiny scales arranged like roof tiles. There are more than 170,000 lepidopteran species in the world, but many are small and unassuming. The best known are of course butterflies, comprising around a hundred large, diurnal species that are often beautifully colored and patterned. The nocturnal species are known as moths.
Flies, or dipterans, include not only species we commonly call flies, such as blowflies and horseflies, but also mosquitoes, gnats, and crane flies. Their Latin name derives from the fact that they have only two wings (di means “two,” ptera means “wing”), whereas insects normally have four, as mentioned earlier. In dipterans, the hind wings have been repurposed as small, club-shaped gadgets that help them achieve balance in flight. We know of at least 150,000 species of dipterans worldwide.
Most people are less familiar with the order of true bugs (Hemiptera), even though it encompasses more than 80,000 species. The group includes a variety of different-looking insects, such as shield bugs, stink bugs, bedbugs, pond skaters, cicadas, aphids, and scale insects. They all have beak-shaped mouths that serve as a kind of drinking straw they use to suck up their food—often sap from plants, although a few are predators or bloodsuckers. So although we commonly use the word “bug” to describe any sort of tiny creature, the true bugs are a specific group of insects.
And just so you know: spiders aren’t insects. They belong to the same phylum, Euarthropoda, but a separate class, Arachnida, which they share with other creatures such as mites, scorpions, and daddy longlegs (known as weaving women in Norwegian because they move two of their eight legs as if they were pushing a shuttle to and fro across a loom).
Millipedes, centipedes, and wood lice aren’t insects, either. To take the simplest hallmark, they all have too many legs and belong to various other groups of invertebrates. Nor are the supercute springtails insects, despite having six legs, although they are nearly insects. That said, insect researchers are huge fans of a teeming multilegged community, so springtails and arachnids are often allowed into the fold when we discuss insects anyway. That is true in this book, too.