The Insect Crisis: The Fall of the Tiny Empires That Run the World 
by Oliver Milman.
Atlantic, 260 pp., £16.99, January, 978 1 83895 117 7
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Silent Earth: Averting the Insect Apocalypse 
by Dave Goulson.
Vintage, 328 pp., £9.99, May, 978 1 5291 1442 3
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Insects don’t get a great deal of airtime in Rachel Carson’s Silent Spring. The book that exposed the harmful effects of DDT on fish, birds, livestock and people had surprisingly little to say about the creatures the pesticide was intended to harm, except that they were starting to develop resistance – in other words, the case for spraying poison indiscriminately wasn’t compelling even on its own terms. ‘However rapidly technology may invent new uses for insecticides and new ways of applying them,’ Carson wrote, ‘it is likely to find the insects keeping a lap ahead.’

Sixty years on, that doesn’t seem like such a safe bet. Carson’s work led to the banning of DDT in agricultural settings around the world, but it was replaced by a new generation of pesticides, the most widely used of which, neonicotinoids, are hugely more toxic to insects. The first neonicotinoid came on the market in 1991. By the end of the decade, anecdotal evidence suggested that insect numbers were declining rapidly. People were making fewer stops on long car journeys to scrape bug spatter from their windscreens. They were seeing fewer ‘moth snowstorms’ in their headlights, fewer fireflies in their gardens after dark. These observations weren’t scientific, but they indicated, at least to some, that insect numbers were collapsing.

Almost a million species of insect have been identified – around 90 per cent of all known types of animal – but it’s thought there may be up to nine million more. The Smithsonian Institution puts the total number of individual insects at around ten quintillion, or ten million million million, almost 1.3 billion of them for every human. Ants alone outnumber us by something like a million to one, and if you squashed them all into a gigantic ant-ball, they would equal us in mass. Until very recently, the painstaking work required to monitor insect populations didn’t seem like the best use of entomologists’ time. It was often left to groups of amateurs, such as the Krefeld Entomological Society, which has been catching flying bugs in malaise traps since the late 1980s. When the society analysed its data in 2016, it found that the total weight of its haul had fallen by 75 per cent over the previous 27 years. The account of these findings, published in the journal PLOS ONE, prompted much hand-wringing (as well as the unlovely coinages ‘insectinction’ and ‘insectageddon’). Critics pointed out that all the data came from Germany, and only from those parts of Germany where the researchers had expected to find large insect populations: perhaps local factors were to blame?

Subsequent studies, however, have confirmed the downward trend. Figures for the rate of decline vary wildly: the number of terrestrial insects may be falling by less than 1 per cent or by as much as 2.5 per cent a year. (Freshwater insects seem to be doing better, with their numbers increasing by a bit more than 1 per cent a year.) The extent of the overall decline hasn’t been settled either – there’s still no data from large parts of Africa, Asia or South America.

The authors of two recent books on insect decline, Dave Goulson, a professor of biology at the University of Sussex who was involved in the Krefeld study, and Oliver Milman, an environment correspondent at the Guardian, are both convinced that we can’t afford to wait for more facts to emerge. Their books cover much the same ground, though with different emphases. Both make the point that insects are an integral part of all terrestrial and freshwater food chains: if their numbers were to drop below a certain unpredictable point, it wouldn’t be long before most lizards and amphibians starved to death, along with many of the smaller birds and mammals. This would, in turn, cause problems for the larger birds and mammals that feed on them. Without insects to pollinate them, many plant species would become extinct, which would mean the disappearance of most fruits and many vegetables, leading to widespread malnutrition among humans. Spices, coffee, wine, chocolate and honey would be gone too.

Insects are also involved in the breakdown of organic matter. It isn’t easy to do without them, as early cattle farmers in Australia learned: the native dung beetles, used to the harder consistency of marsupial dung, weren’t able to break down cowpats, which by the late 1950s were advancing across the country at a rate of two thousand square kilometres a year. Just imagine that on a global scale. ‘For the majority of humanity,’ Milman concludes, ‘the loss of insects would be an agonising ordeal eclipsing any war and even rivalling the looming ravages of climate breakdown.’

A major cause of the decline, Goulson and Milman agree, is the change from agriculture to agribusiness in recent decades. Along with the industrial use of pesticides, one of the biggest factors driving the insect crisis is the destruction of complex habitats, often to make way for single crops (especially soya bean and palm oil) and the rearing of livestock (especially cattle). Goulson provides some statistics: ‘Between 2000 and 2012 we lost 2.3 million square kilometres of forest worldwide – an area greater than the combined size of the UK, France, Germany, Spain, Portugal, Belgium, the Netherlands, Italy, Switzerland, Austria, Poland, Ireland and the Czech Republic.’ The result is that something like 135 rainforest species are being driven to extinction every day. Meanwhile, cities and suburbs are also becoming less hospitable to insects. In 2005 Nasa scientists used satellite imagery to calculate that lawns (including those in public parks and golf courses) covered 128,000 square kilometres of the United States: a stretch of diminished ecosystem greater than that devoted to any other single crop. ‘Plants useful for insects do sprout in this otherwise sterile environment,’ Milman writes, ‘but are often deemed weeds and quickly snuffed out by assiduous homeowners.’

Full restoration of endangered species isn’t a realistic ambition. But insects are adaptable and reproduce quickly; there are some simple measures that could improve their chances of survival. Milman describes the case of the tiny, greenish-brown butterfly known as Saint Francis’s Satyr, which was believed to be extinct until a few thousand were discovered in the artillery range at Fort Bragg, North Carolina. ‘To the shuddering background noise of 181 kilogram bombs, the butterfly happily flits around the firing range.’ In other words, a simulated warzone provides them with a more attractive habitat than almost anywhere else in the US. A scrap of land with a variety of flora, free from chemical interference, is pretty much all that insects need. It wouldn’t be too hard to create more of these, ideally joined up into a global network of insect-friendly corridors running between farms and urban areas. The conservation group Buglife has proposed a 3000-mile network of such corridors across the UK.

What’s preventing this from happening? One reason is that ‘the majority of people don’t much like insects,’ as Goulson puts it. It’s hard to imagine the World Wildlife Fund campaigning to save the titan beetle – a reddish-brown longhorn, the length of an outstretched hand, whose jaws are strong enough to snap a pencil in half – with quite the sentimental appeal of its campaign to save the giant panda. Freud and Jung both noted the strange hold insects had on their patients’ imaginations, the frequency with which they arose as the subject of phobias. We see these anxieties in Kafka’s ‘monstrous vermin’, Dalí’s skulking grasshoppers and swarming ants, Frida Kahlo’s grizzled caterpillars, David Lynch’s Blue Velvet and David Cronenberg’s The Fly.

Goulson finds our aversion to insects mysterious. He has a point: outside malarial zones, the danger they pose to human health is limited. People living in the Global North probably have more reason to fear arachnids, the family that includes spiders, ticks and scorpions. In the UK, you’re about as likely to get trampled to death by a herd of cows as you are to die from a bee or wasp sting. Flies and cockroaches can be carriers of harmful bacteria, but so can unwashed towels and undercooked eggs. The difference is behaviour. Insects dart suddenly towards you. They lurk in crevices; they take to the air. They can seem indestructible. It probably isn’t true that cockroaches could survive a nuclear explosion, but they can withstand much higher levels of radiation than humans; fruit flies can withstand even more. Despite the ongoing collapse of insect populations, some of the hardier species – cockroaches, locusts, bedbugs – are almost certain to outlast us, just as they weathered the event that killed the dinosaurs.

Their alien appearance doesn’t help. All insects have a head, a thorax, an abdomen and six legs, but beyond this basic structure there is the potential for infinite variety. One species of Ecuadorian treehopper has five hairy balls sprouting from its head, in an apparent effort to mimic symptoms of fungal infection. The giant wētā, a native of New Zealand, looks like a cross between a grasshopper and a woodlouse and weighs more than a sparrow. The lives of insects are often downright creepy. Twisted wing flies spend most of their existence crammed inside the bodies of bees and wasps, occupying up to 90 per cent of the abdominal space. The female Brazilian book louse penetrates the male with a sort of barbed penis to harvest his sperm, a procedure that takes days. This is mere foreplay to stick insects, which can remain locked in coitus for weeks. Certain wasps feed their young in horror movie fashion. First they drive their stinger into the part of a cockroach’s brain that controls the escape reflex; then they lead the victim back to their nest, where they lay a single egg on top of it, wait for the offspring to hatch and then watch them eat it alive. Even the more attractive insect species can be disturbing when they swarm. I once encountered a huge aggregation of ladybirds on the North Norfolk coast. They spattered themselves against the windscreen in such prodigious numbers that even with the wipers on I could hardly make out the road; when I stepped out of the car their heaped bodies crunched underfoot. I’ve since discovered that the collective term for ladybirds is ‘a loveliness’. It’s not the word I’d have chosen.

Milman argues that our dislike of insects is largely cultural. Small children, he points out, are often ‘fascinated by insects and want to interact with them’, but are ‘taught to fear … when the reverse should be the case’. Aside from their importance as pollinators and decomposers, he believes that insects could help solve many global challenges. They’re a cheap and sustainable source of nutrition: the UN’s Food and Agriculture Organisation estimates that two billion people – concentrated in Asia, Africa and South America – have insects as part of their diet. They may have properties highly valuable to a post-antibiotic world: scientists at the University of Zurich have suggested that thanatin, a natural antibacterial agent produced by the spined soldier bug, could offer the basis for a new class of drugs. Many cockroaches and beetles are thought to have medicinal properties and Milman wonders whether other insects might too: ‘The unseen loss of insects, the sort of Centinelan extinctions that confound our understanding of exactly what we’ve banished from the living world, means we may have carelessly burned through revolutionary medicines via the mundanities of farming, urban development and other staples of modern life.’

Goulson doesn’t have Milman’s knack for rousing cadences and shapely phrases, so it’s brave of him to have a go at conjuring the Cormac McCarthy-style apocalypse that awaits us if insect numbers continue to plunge (‘Ah, how I miss chocolate. I have tried to explain how it tasted to my grandchildren, but of course it is impossible’). What he lacks in elegance he makes up for in radicalism. Where Milman largely relies on anthropocentric arguments for the value of insects, Goulson dispatches those arguments in a single dutiful chapter, before coming clean: ‘If I’m honest, their economic value has nothing whatsoever to do with why I try to champion their cause. I do it because I think they are wonderful.’ Descriptions of his favourite insects occur throughout the book: the bombardier beetle, whose defence mechanism involves ‘spraying near boiling and toxic benzoquinones’ from its rear ‘with an audible “pop”’; the honeypot ant, which consumes so much nectar that it becomes ‘grotesquely inflated’ and immobile before being used as a nectar tap by the rest of the colony during the lean months of the year. He describes metamorphosis as a process ‘as magical as any frog-to-prince transformation’:

Imagine you are a full-grown caterpillar. You digest your final meal of leaves, then spin yourself a silken pad to hold you tight to a stem. You then split out of your old skin, revealing a new, smooth brown skin beneath. You no longer have eyes, or limbs, or any external openings except tiny holes called spiracles to allow you to breathe. You are entirely helpless, and will remain so for weeks, perhaps months … Inside your shiny pupal skin your body dissolves, the cells of your tissues and organs preprogrammed to die and disintegrate, until you are little more than a soup. A few clusters of embryonic cells remain, and these proliferate, growing entirely new organs and structures, building you a brand new body. Once it is ready, and the time is right, you split open your pupal skin and underneath have grown another one, this time complete with large eyes, a long, coiled proboscis for drinking and beautiful wings covered in iridescent scales that you must inflate by pumping blood into their veins before they harden.

With an encomium like this, it’s easy to see how much smaller and duller the world would be without a wide variety of insect life, even if humanity did manage to cling on. But Goulson goes much further than that. Insects predate human life by almost 350 million years; they now exist in every freshwater and terrestrial ecosystem. As far as he’s concerned, it’s their planet. Even talking about the wonder they afford is solipsistic. ‘Why should the existence of slugs or midges need to be justified?’

He imagines a future in which pesticide-free urban areas are surrounded by ‘small, labour-intensive biodynamic and permaculture farms producing abundant fresh fruit and veg’, all of it ‘pollinated by bees, wasps and hoverflies and guarded against pests by an army of ladybirds, earwigs, soldier beetles and lacewings’. Farms in rural areas would comprise ‘small numbers of livestock, many more trees than at present, minimal use of pesticides and a stronger focus on sustainability and soil health than on maximising yield’. He would also like to see lynx, wolves and bears roam free. There’s a snag, though. ‘Crucially,’ he writes, ‘humans [would] not regard their own needs as having priority over all others.’ A world that works for insects is one in which humans put their own short-term interests aside on behalf of some pretty unpopular species. That future doesn’t look imminent. Meanwhile, scientists in the Netherlands are already developing robot bees.

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