How humanity is changing the world’s insects

People have been transforming the world’s insects for millennia – but as the Anthropocene gathers pace, the process is speeding up.In a factory in Japan, a million farm animals are being carefully tended. Just a few days before, they twisted themselves out of their sand-like eggs and into the wide world. Now they’re minuscule walnut-brown caterpillars – mere commas on the neatly folded sheets of white fabric they inhabit. Their conveyor belt “mother” is diligent, if slightly detached: three times a day, she unceremoniously dumps a layer of reconstituted mulberry leaf mulch on top of them. It is quickly devoured – and within a few weeks, they graduate to eating fresh mulberry leaves, which are scattered over long, flat tables as though they’re a dish being garnished. Finally, when the caterpillars are as plump as human fingers, with creamy, papery skin, it’s time for their big moment: they’re shovelled onto cardboard racks, where each one spends the next few days weaving itself into a delicate white cocoon. These are silkworms – and up to a trillion are raised every year. In fact, though they’re conspicuously absent from children’s storybooks, agricultural fairs and farmyard tales, they are the second-most abundantly cultivated animal on the planet, after honeybees. They’re also widely considered to be domesticated – part of the exclusive pantheon of early human partners which helped our species to conquer the world.  Around 7,500 years ago, when modern horses were still roaming the windswept steppes of southwestern Russia and turkeys were wild animals strutting North America’s woodlands, silkworms were plucked from mulberry bushes in central China to begin their relationship with people. In the millennia since, they’ve undergone changes at every level – genetically, behaviourally, physiologically, and even aesthetically. And they are not the only insect to do so. Humans are currently farming a wider variety of tiny insect livestock than ever before. Across the globe, mealworms swarm in shipping containers, crickets scramble around makeshift egg carton enclosures in homes, and bees tour entire countries, neatly packed into portable hives. With each passing generation, they’re being transformed: the more dependent we become on them, the more they depend on us.Domesticated silk moths produce larger, whiter cocoons than their wild ancestors (Credit: Getty Images)But as insects and humans have become closer, very few people have noticed – domesticated insects are still radically understudied, and the consequences are only just starting to be considered. From concerns about vanishing wild counterparts to disease and an almost total lack of welfare standards, the process can have some unpleasant side effects. How are these creatures adapting to life with humans? And should we be paying more attention to what we’re doing? A strange mutant    To fully appreciate how dependent silkworms have become on their human overlords, it helps to look at the adults. For the vast majority of these hungry little caterpillars, their journey ends abruptly – and tragically – when their cocoons are tipped into hot water during the first step of silk processing. The developing moths inside are boiled alive and their cosy shelters become their tombs. A few lucky individuals, such as those raised by curious pet owners (the caterpillars are popular as reptile food) or destined to produce the next generation, are allowed to develop to the next stage of their life cycle. Once inside their cocoons, first they step out of their papery skin and change into pupae, the intermediate stage between a caterpillar and a moth. Over the following 10-14 days, they deconstruct their entire bodies, cell by cell, and reform. The adults emerge from their cocoons head-first, like human babies – at first they’re soaked in fluid, but as they clamber out, soon it’s clear that these are no ordinary moths. With enormous, cartoonish black eyes, thick, feathery antennae that flop down like the ears of a spaniel, and bodies covered in poodle-white fluff, they look more like Pokémon characters than real animals. Their modest wings, out of proportion with their large bodies, almost resemble the stuck-on kind children wear to parties. In contrast, the domesticated silk moth’s wild ancestors are entirely unremarkable to look at – with brown, mottled colouring, significantly smaller bodies, and large wings. If one landed next to you, it would look like a regular garden-variety insect.   The captive silk moths are so coddled, they’ve entirely lost the ability to fly. During their week-long adult lives, they have no way of escaping predators and can only seek out a mate on foot – they’re entirely dependent on humans to place males and females near one another.Vast crop monocultures require staggering quantities of pollinators – so it’s routine to take millions of honeybees on tour, packed into the backs of trucks (Credit: Getty Images)Domestication is a granular process, rather than an end point, explains Thomas Lecocq, an associate professor in animal biology and ecology at the University of Lorraine, France. And silk moths are extreme examples of what happens when it runs on for millennia: they cannot complete their life cycle without us.   “In fact, it’s a kind of continuum of interaction between humans and the animals… and within it you can say ‘I reached this level of domestication, because I’m able to complete the whole life cycle of the organism in captivity’,” says Lecocq.         These clumsy “sky puppies”, as some have nicknamed them, aren’t just unable to fly – they’re more sluggish, have a worse sense of smell, smaller brains, and even different gut microbiomes than their wild counterparts. Crucially, domesticated silkworms also produce different silk. Silkworms weave their soft, perfectly ovoid cocoons using their mouthparts, which secrete a protein-rich liquid that hardens as it emerges. So the caterpillars wave their little heads around, literally drawing them in the air. Eventually they end up with a fuzzy cocoon made from a single unbroken strand of silk around 915m (3,300ft) long – just under a kilometre. In its raw form, silk is coated in a kind of glue that stiffens it and makes it coarse to the touch. Not only do domestic silkworms produce larger, whiter cocoons, they make much less of this protein – sericin – which has to be removed as part of the manufacturing process. The wild Bombyx mandarina moth has been so transformed, its domesticated cousin, Bombyx mori, is now a different species. But not all domesticated insects have undergone such conspicuous changes. A tricky question At a farm in Wales, a queen has arrived. There’s no marching band, security, or patriotic crowd – in fact, this monarch has suffered the indignity of being transported via special delivery, inside a plastic carton. She has, at least, been allowed a team of courtiers, waiting patiently alongside her in the passenger zone. At the other end, there’s a large pile of icing sugar. She is, of course, a honey bee – a member of the noble Buckfast breed – and she and her attendants have arrived to improve the productivity of an existing hive. After she’s been unpacked and placed among her new subjects, she will eat her way through the plug of icing sugar and exit into her bee-palace.Domesticated silk moths are often considered cuter than their wild ancestors – but this has happened entirely by accident (Credit: Alamy)In fact, though many people view bees as wild animals, honey bees are anything but. They’ve had a relationship with humans for over 9,000 years, since the very first farmers began collecting honey and beeswax, and possibly even domesticating them. In the following millennia, humanity’s enthusiasm for these animals continued. The Ancient Egyptians believed bees descended from their Sun god, and housed them in piles of hollow clay pipes. In 2015, archaeologists unearthed a mysterious clay object at a Mayan site, which may have been an ancient beehive – suggesting that they, too, kept the insects, long before Western colonists arrived. Meanwhile, it’s possible that a certain favoured species may have been imported into the Jordan valley to replace the region’s native honey bees as early as the 10th Century BC. Perhaps the most enthusiastic beekeepers were medieval monks. Wearing protective outfits that could easily be mistaken for Halloween costumes – white hooded robes with blank, circular coverings of straw over their faces – they kept bees in woven hives and sold honey or mead to support their monastic activities. But despite thousands of years of beekeeping, when scientists looked at the genomes of honey bees in 2012, they found something unexpected. Rather than having lower genetic diversity than their wild ancestors – as most domesticated animals do – captive honey bees actually had more. What was going on? Today the most widely cultivated honey bees, Apis mellifera, can be found wild in Africa, Europe and Asia. There are many subspecies scattered across the globe, which are adapted to different regions – European bees are better at surviving cold winters, while African bees are more aggressive. Humans have been shaping honey bees for centuries – transporting them vast distances, selecting those with the most desirable traits and crossing different varieties together. But the lines between wild and domestic populations have always been blurred, mostly due to a quirk of the way they reproduce.Scientists are developing a futuristic new generation of silkworms that can produce metallic silk or the super-strong kind from spiders (Credit: Getty Images)Honey bee colonies are feminist strongholds – almost exclusively composed of sisters and half-sisters, who form the workers, together with their mother, the queen. The queen mates just once in her adult life, when she first leaves home. She flies off to find a gang of hopeful males at a “drone congregation area” – mysterious locations where hundreds of drones loiter in the air, waiting for females to arrive. There the queen will mate with 15-20 partners, and bank the sperm for later use. Every subsequent bee in her colony will be a descendent of these pairings. If you’re trying to domesticate an insect, naturally this system presents a problem. The congregation areas are composed of both wild and human-bred individuals, so queens often end up mating with both. This means that no population of honeybees is exclusively domesticated – and farmed colonies will regularly fly off and establish themselves in forests. “I’ve done experiments on this, and if you release domestic populations they survive equally well as feral ones,” says Benjamin Oldroyd, a professor of behavioural genetics at the University of Sydney. These hybrid pairings also mean that, despite 9,000 years of attempting to adapt honey bees to human requirements, the ones we farm aren’t exactly cuddly. The slow progress is especially stark when you look at mammals that began their association with humans at around the same time – while today some cows will act like puppies if you let them (don’t try this at home), their wild aurochs ancestors were notoriously bold and aggressive.   In fact, for almost a century, the most influential technique honey bee farmers could adopt was hybridisation, a process pioneered by the Benedictine monk Brother Adam at Buckfast Abbey in Devon – which is home to 13 monks to this day. Following in the footsteps of another famous monk with an interest in genetics, Adam developed the disease-resistant “Buckfast bee” in the early 20th Century by crossing subspecies with desirable traits from different regions.Farmers routinely swap out honeybee queens who aren’t productive enough. Introducing the new ones is risky – they have to be accepted by their new workers (Credit: Getty Images)With such close ties between wild and captive honey bees, it might seem like they’re not really domesticated at all. However, Lecocq believes this is not the case. There are some populations for which humans control the majority of the life cycle, he explains – and others, such as the Buckfast breed, have been selectively bred into existence. “So yes in my mind, we can say that honey bees are currently undergoing the domestication process,” he says.  But if wild populations are still influencing domestic ones to this day, this raises the question – is the opposite happening, too? “This is a bit of a conundrum,” says Oldroyd. In Australia, the most common wild honey bee is the British Black – a variety that was dominant across large swathes of Europe for millennia, before being almost wiped out by disease around the time of World War One. Though only recently rediscovered in Britain, the bee has continued to thrive in the Australian outback, where it was introduced by European colonists. Oldroyd explains that these bees must be mating with domestic ones – which tend to belong to other European breeds today – regularly, but: “No-one knows. It is a curious thing that you don’t see much gene flow out of the domestic population and into the feral.” A new wave However, as new practices emerge, this may be about to change. Enter artificial insemination – a technique that’s becoming increasingly popular with bee farmers worldwide. It’s exactly as fiddly and invasive as it sounds. First, several male honey bees are killed and milked for their semen by squeezing their abdomens – drones automatically die a violent death as part of the mating process, so this pre-empts the inevitable. Next the queen bee is immobilised with a whiff of carbon dioxide, and the sperm mixture is injected into her genitals. One company has even invented a bee-insemination machine to make this part easier.Domesticated honeybees are intensively managed, with their human keepers controlling their location, diet, health – and increasingly, their reproduction (Credit: Getty Images)After thousands of years of controlling the female line, but not the male, now farmers can have full control over honey bee reproduction – with potentially unprecedented results. It’s already common to actively select for queen bees with more docile manners, so they could become even friendlier. And honey bees are not the only insects about to get a major makeover.    “Most of the domestication [of insects] has occurred quite recently, in the last decades – in a kind of new wave,” says Lecocq. There’s a major reason for this: humanity has never been more reliant on insects to produce the food we eat. Though their efforts go largely unnoticed, each year the world’s bumblebees, solitary bees, hoverflies, wasps, moths, butterflies, and beetles collectively pollinate 84% of the crops we grow. At the moment, many of these insects are wild, and amid a major “insectageddon” – a global mass extinction of these strange life forms – our dependence on them is increasing. At the same time, there’s been a recent surge of interest in insects that can provide natural pest control, such as ladybirds – it’s estimated that just one of these formidable predators can devour 5,000 aphids in its lifetime. Then there’s edible insects, already a delicacy in many parts of the world, and which may become an increasingly important source of protein as the global population grows.   Amid this demand, farmers have begun domesticating some unlikely species. Take the humble bumblebee. Until the 1980s, there was no reason to breed them in captivity – they don’t produce honey – so they could only be found in the wild, nesting under sheds, long grass and old rabbit holes. Bu