Tiny Killers The Secret World of Insects

What could be more peaceful than a patch of green bathed in sunlight? Let's move closer to this orchard that's far from everything, somewhere in the Austrian Alps. This is the ideal place for abundant biodiversity to flourish. And at the heart of this universe, a nearly invisible world is hiding. The world of insects. Each species, which is a part of it, lives in perfect harmony with its environment and knows how to best use nature's resources. Yet behind its peaceful appearance lives a ruthless world, where millions of tiny creatures die every second. Here, danger is ever-present, and for every inhabitant, each day could be their last. Eat or be eaten. The rule is simple, and each creature is constantly fighting for its survival. The inhabitants of this world are marvels of adaptation, the result of millions of years of natural selection. Some species have developed survival skills and exceptional defense mechanisms. Others have killing techniques of unimaginable cruelty. Here, survival is learned from the earliest moments. On the underside of a leaf, five small eggs are preparing to enter this ruthless world. Their mother deposited them here six days ago. Defenseless, just hatching is a small miracle. These are the larvae of the scarlet lily beetle. This insect has developed an unpleasant but effective defense mechanism. Larvae barely out of the egg begin to devour the leaves, gorging on cellulose. Little by little, they cover themselves with their own excrement. Are they less appetizing to predators? Protected against dehydration or disease? It is still unclear the specific benefits of this defense mechanism. But as disgusting as it seems, it allows them to survive until they begin their metamorphosis. In the insect world, metamorphosis defines life's pace. A larva becomes a caterpillar. A caterpillar becomes an adult insect. The beetle is therefore working towards the most radical transformation it will undergo in its life. For this, it burrows into the ground and creates a cocoon with saliva and soil. The transformation will not be complete until the following spring. The rays of the springtime sun begin to warm the earth of our Austrian orchard. On these few acres, life is finally emerging from its winter slumber. An adult beetle emerges from the loose soil, completely different from the larva that was buried there some months earlier. Feeding exclusively on plants, this robust but harmless insect is protected by an exoskeleton. This hard shell may protect it from the attacks and dangers that this tiny world holds. Meanwhile, much higher up, in the branches of an apple tree, another insect is also having dinner. This is the apple blossom weevil. It is a weevil familiar to farmers for the damage it causes to crops and fruit trees. Its secret weapon is its long, solid rostrum. At the end of this appendage, it has a pair of small mandibles. Thanks to them, the weevil is capable of devouring plants from the inside and getting to the most hidden reserves while remaining on the surface. And unlike the scarlet lily beetle, which abandons its eggs outside on a leaf without any protection, the weevil is determined to offer the best chance of survival to its children. With its snout, it digs a canal to the heart of an apple flower bud and deposits an egg. There, protected from the outside world, this little egg will hatch. The larvae of the weevil, squatters from the beginning, begin feeding on the delicate flesh of the flower bud. Externally, the bud turns brown, shrivels and will never become an apple blossom. Instead, it looks like a clove. And once the larva has accumulated enough energy from devouring the bud, it begins its final transformation to become an adult weevil. In this universe, living means causing death. There's no need to be a predator for that. Peaceful insects like the weevil or the beetle are able to devour plants or mutilate trees. And these are not the only species that feed on plants. Far from it. The climate in our orchard is temperate, with hot summers, mild winters and abundant rainfall ideal conditions for many plants to grow. On a single acre of pasture, grass, bushes and fruit trees represent a mammoth amount of plant matter. For the inhabitants of this tiny world, the smallest plant is the size of a skyscraper. So, it's no surprise that nearly one million insect species are phytophagous or plant-eating specialists. Some, like the beetle and the weevil, eat the flesh of a plant. Others prefer to suck its very lifeblood. Attracted to overripe apples that have fallen to the ground and thanks to their long, flexible proboscis, butterflies have flocked to sip the sweet juice that the fruit exudes. Above them, in the branches of the apple tree, scylla suck the sap directly from the fruit tree, thanks to a rigid snout that they insert into the thin bark. But among these plant vampires, there is one family whose appetite exceeds all others. The aphids. They are tiny, but numerous, and are able to infest an entire apple tree. A single apple leaf can be home to hundreds. Like the blood in a human body, plant sap is often pressurized. Aphids have a spike-shaped mouth that they insert directly into the plant. Due to the pressure, the sap goes directly into their stomachs, without any sucking action. Aphids try to extract proteins from the sap that are vital for their growth. But the sap, mainly rich in sugar and water, contains very little of these proteins. Aphids are thus condemned to swallow a constant flow of liquid and dispose of the excess sugar at the same time. The insect is a permanent digestion machine. As it eats, a bead of the meal's residue forms on its anus. These small drops are called honeydew. And ants are crazy about this juice that contains highly concentrated fructose, glucose, and all other kinds of sugars. For this worker ant, lucky enough to encounter a colony of aphids eating, it's a smorgasbord. It runs from one drop of honeydew to another to gather as much of this unexpected energy resource as possible. The waste of one species is sometimes the delicacy of another. The ant's appetite is also beneficial for the tree, because if the honeydew falls on the leaves, it causes the appearance of sooty mold fungi, which asphyxiates the leaves. This is why farmers consider the aphid a pest. Its presence can be fatal to crops, especially because the aphid has a particularly effective reproduction method. On the trunk of our apple tree, the first aphid eggs of the year hatch. However, it's actually only female aphids that emerge. Here, they grow, molt to free themselves from their exoskeletons that have become too small, and are finally ready to reproduce. And yet, without any males on the horizon, they don't lay eggs, but give birth to females that are nearly adults. In fact, aphids practice parthenogenesis. Reproduction without fertilization. Every female is a clone of her mother, and can already give birth in turn. That's why, apart from diseases, aphids are the kings, or rather, the queens of all pests. In the heart of these few acres, there are already the first ingredients for a miniature universe. Fruits, leaves, flowers, and sap. Plant-eating species that have evolved to adapt to their resources. Adopting highly specialized anatomical structures, and sometimes seemingly odd behavior. In this Garden of Eden, nothing is as peaceful as it seems. Even the plants are able to defend themselves. Some, infested by aphids, emit pheromones, a scent that attracts a different type of inhabitant in this tiny world. The entomophagous parasites. The insect eaters. There are many that feed on aphids. This is the most terrible of all the predators that have sensed the plant's distress signal. Innocent looking enough, the ladybug is actually a hungry beast. None can overcome an aphid colony like it can. Even its larvae savor this prey, served up on a silver platter. Lurking near this carnage is a completely different predator. A small wasp, which has an even crueler fate in store for the surviving aphids. Here is Aphidius wasp. A parasitic wasp in the Ichneumon family. Rather than feeding on aphids, it prefers to use them as incubators. It stealthily approaches the aphid. Waits for its prey to be distracted. Turns its back. Then it deploys a long stinger through which it implants a single egg into the aphid's body. The aphid is then doomed. The egg becomes a larva in the very bowels of the aphid. Then the larva spins a cocoon. And it is at this point that the aphid stops moving and finally dies. The exterior blackens and dries. And after a few days, climbing out from this grim shell, a little wasp leaves its sarcophagus and is ready to parasitize other aphids. Aphids are excellent hosts. But a cousin of Aphidius, the species Cortesia glomerata, has pushed the art and horror of parasitic behavior to its highest level. Perched on a blade of grass, this little wasp has a very unusual hunting technique. Its main weapon is patience. It stalks its prey even before they hatch. At the moment, the larvae of the Pyrus brassica are still safe in their eggs on the back of a cabbage leaf. But not for long. Before even worrying about this predator, the larvae are undertaking their first struggle for their lives. Thanks to their already powerful mandibles, they eat the thin wall of the egg. It only takes them a few minutes to get out of the tiny structure. Finally, here are the larvae of the butterfly, Pyrus brassica. Newly hatched, the larvae begin to devour the rest of their eggs. Then they start eating the leaf on which they were laid. With a voracious appetite, the Pyrus can destroy entire crops. But for now, the larvae are helpless. Focused on their first meal. This is the moment our killer wasp was waiting for. Cortesia approaches these vegetarian larvae without the slightest risk. It takes the time to aim and pierces the soft flesh. Its weapon is not a stinger, but an auger. A strong appendage able to penetrate the bodies of other insects. The auger is actually a canal through which the wasp can lay its eggs directly inside its prey. The attack is swift. Cortesia continues tirelessly parasitizing as many larvae as possible. It can leave up to 50 eggs in each of its victims. Then the parasitic wasp flees the scene. Leaving its victims alive and well. But carrying small time bombs. The moth larvae quickly recover from this unpleasant experience. And they have not lost their appetite. Like all caterpillars, they want to grow as fast as possible. To store as much energy as they can to transform into butterflies. But those who have been infected by Cortesia will die long before. In the apparent calm of this idyllic landscape, nobody would be able to imagine the drama brooding under the orchard's tall trees. For a fortnight, pyrus caterpillars continue to eat, continue to grow and become fat, juicy caterpillars. But as they prepare to become beautiful white butterflies, those that were attacked at birth show signs of fatigue. Weakness. Their bodies twitch. Their movements slow. Until the day when dozens of larvae rip the caterpillar open, emerging like little aliens from their host's body. These are the larvae of the Cortesia glomerata wasp, which also grew during this fortnight. They fed on the caterpillar, gradually eating their host, while taking great pains to spare its vital organs. Just after the parasitic larvae arrive in the open, they begin spinning a cocoon without concern for the dying caterpillar. This pyrus caterpillar will never become a butterfly. But after devouring the caterpillar from the inside, the Cortesia larvae have gained enough energy. In the cocoon, they start to transform. And after a week, the small larvae have changed radically. These are adult wasps, making their way outside. One by one, the siblings come out, ready to reproduce. Young males do not waste a moment. The first female wasp, which shows the tip of its antenna, is an attractive choice. Attacked on all sides, she is quickly fertilized and can leave, like her mother before her, to look for butterfly larvae to carry her eggs. And the cycle begins again. The chilling parasitism of Cortesia wasps is so effective that some females can eradicate an entire population of pyrus in a few generations. The reproductive method of these insects seems cruel, repulsive. But there is no cruelty in nature. Cortesia has simply developed a very effective parasitic technique, making it the most fearsome and murderous mother in the insect world. The balance of this invisible world has been built over millions of years. Harmful species like the aphid could not have proliferated unchecked, or there would be no plants today. Plants have evolved to defend themselves. Other insects have evolved to take advantage of this ubiquitous aphid, either for food or to hide their eggs. And aphids have continued to evolve to reproduce ever faster. In nature, evolution is an arms race. And it's not just the insects that are battling it out. On a nearby branch of the great phylogenetic tree of life, there is the class of arachnids. Spiders, scorpions and mites. Among these animals, we can find the most varied hunting techniques in this invisible world. Although they are distant cousins, do not confuse insects and arachnids. Insects have a body divided in three parts. Head, thorax and abdomen. They also have six legs, antennae, mandibles and often two pairs of wings. Arachnids' bodies have two parts. The head and thorax are fused into a cephalothorax. They have eight legs, but have neither antennae nor wings. Their mandibles become venomous fangs called calytheri. Literally, armed to the teeth. Arachnids are the natural-born predators in this invisible world. Especially with spiders, the art of hunting has been highly refined throughout their evolution. Some are camouflaged to surprise their prey, or they wait for the smallest movement and then jump on the first insect that has the misfortune to go within the reach of their calytheri. And most use traps like webs of sticky silk. But some arachnids simply prefer to pursue their prey. At the foot of an apple tree, on the ground, protected by a thick cover of vegetation, a different kind of arachnid has begun hunting. This strange animal looks like a scorpion, yet it has no tail or stinger. But its ferocity and appetite make it a formidable fighter. It's called the pseudoscorpion. Quick as lightning, it attacks the smallest insect that crosses its path. Caught in the vice, the torture of its victim is just beginning. The pseudoscorpion hides dreadful venom glands in its pincers. When its sharp extremities pierce the shell of the insect, it is immediately paralyzed. The predator then plants its hooks into the helpless animal and injects it with highly concentrated gastric fluid. Its bowels are reduced to mush in a matter of minutes. This is when the pseudoscorpion begins its grisly meal. As if it were insect soup, it sucks its dying victim. The hunter is so voracious that it won't hesitate to jump on a second victim, while still sipping on the first. A little further from the canopy, another creeping predator is wending its way. It has more than eight legs, and insects are also its favorite meal. Centipedes, like most millipedes, don't really have a thousand legs, but they do have small pincers called forcibles that can inject an extremely potent venom that is deadly to most insects. But for this centipede on the hunt, the situation will take a different turn. Despite all its weapons, the predator can sometimes be the victim of a single beetle, well protected by its chitin armor. It is the unchanging lesson of this tiny world. No one is safe. Even the most ferocious scorpions, even the most nimble spiders, or the most venomous centipedes can go from being the hunter to the hunted in an instant. In these few acres of wilderness, daily life is made up of opportunities and unfortunate encounters. Here, murder also benefits a third category of inhabitants. The garbage collectors of the invisible world. All of these plants, mostly devoured by plant-eating insects like aphids, all of the bodies of these insects, emptied by parasites or half-eaten by predators, represent a phenomenal amount of nourishment. And as evolution is firing on all cylinders, some of the inhabitants of this microcosm are specialized in the consumption of this decaying matter. These tiny scavengers live mostly in the soil. At the foot of an apple tree, we see one of these scavengers making its way between the earthen blocks. Cure is one springtail species. They are very archaic insects. Omnivorous, ceratophysala, feed on both animals and plant remains. But springtails must constantly be on the lookout for predators. And be prepared to abandon their meal at any time. For this, they have a very special appendage on their stomachs called the furcula. Like a little spring, the furcula can unwind and propel the animal into the air in milliseconds. Springtails are tiny, harmless. They feed on waste, food scraps. But evolution has equipped them with a unique asset. Their furcula, that allow them to escape many lurking dangers. Being heavily armed is not enough to survive in this ruthless world. Sometimes, knowing when to flee has been enough for a species to survive throughout the ages. When the light disappears, a legion of grave diggers comes out of the shadows to feast on the corpses left during the day. And when the sun rises again, these nocturnal scavengers return to their lairs and the orchard awakens. In the pastures, on the mountainsides, everything is recycled. And cow dung is an entire ecosystem. And here we find mostly flies of the Diptera order. These species are coprophagous. That is to say, they feed on fecal matter. And for these flies, cow dung is not only a large outdoor buffet. It is also the perfect place to copulate and then lay their eggs. The larvae that hatch in this rich environment can develop, safe from outside danger, while feeding on the fecal matter around them. When the larvae have eaten enough, they are ready to start their final transformation. Like a butterfly's chrysalis, the larvae become pupae, surrounded by a protective cocoon. But to get out, the insect is going to need a very special organ, the telenum. Located on its head between the eyes, the telenum fills with fluid to stretch and burst the cocoon, to finally give birth to an adult fly. The life of these dung-eating insects is not very appetizing. But they play a vital role in the ecosystem because, as scavengers, they recycle organic matter left by herbivores and carnivores. And all this recycled material returns to the ground. Whether on a mountain, in a pasture, or in the shade of fruit trees in an orchard, the smallest blade of grass, as well as the biggest apple tree, need soil in which to plant their roots. With their leaves, plants capture the sun's energy through photosynthesis. But with their roots, they burrow into the ground to extract minerals. In our few acres, if you dig a little, you will discover an inhabitant that's very discreet, but crucial to the functioning of this microcosm. The earthworm. This familiar creature belongs to the Annelida phylum. The earthworm is a soil engineer. It digs relentlessly, swallowing and spitting out earth, creating humus. The top garbage man of the animal world, it digests the last pieces of organic matter to excrete the nutrients and minerals that allow vegetation to grow. The earthworm has a surprising anatomical feature. It's a hermaphrodite, both male and female at the same time. As such, any two worms can always reproduce, regardless of their partner's sex. An ideal ability to perpetuate the species. Here is an earthworm egg. Safe inside, the embryo has slowly transformed. And after four weeks, it has become a young earthworm, finally ready to get out of its cocoon. For now, it's only a few millimetres long, but within a year, it will become an adult, measuring over 30 centimetres long. Like its parents before it, and the millions of fellow creatures that inhabit our orchard, it will work the soil, giving plants the ingredients necessary for growth. These same plants, which feed plant-eating insects, which themselves will feed insect-eating insects, which feed the scavengers. The circle of life goes full circle, and each species has struggled for millions of years to find its place within nature's cycle of life. On average, insects and arachnids are between 100 times and 1,000 times smaller than we. This is why their world often goes unnoticed. But in this tiny world, there is another microcosm filled with creatures 1,000 times smaller than the insects. If you get near a branch of our apple tree and look very closely at the blossoms, you can see unexpected movement. It is the invisible world inside the invisible world. The world of mites. Mites are arachnids, like spiders and scorpions. But they alone form an entire universe, with its own scavengers, herbivores and predators. And as in the insect world, inside the mites world, there's a daily fight for survival. Microscopic killings are no less ferocious than those of the giants around them. These interconnected universes have millions of inhabitants, in only a few acres of a seemingly peaceful orchard. On the surface, nothing gives an indication of the relentless violence and the struggle for survival taking place behind each blade of grass, under every leaf. Yet for millions of years, these wars have been raging, without a sound, without a cry. The species that have survived until today have paid a heavy price to evolution. Whole generations were decimated, so that some survivors, better and better adapted to these extreme conditions, could stand out from the rest and manage to carve out the best possible place in this unexpected battlefield. The smallest ant, the simplest fly, the smallest spider are indeed the descendants of a long line of survivors.