The terrorists' letter arrived at the Mayor of Los Angeles's office on November 30, 1989. A group calling itself “the Breeders” claimed to have released the Mediterranean fruit fly in Los Angeles and Orange counties, and threatened to expand their attack to the San Joaquin Valley, an important centre of Californian agriculture.
With perverse logic, they said that unless the Government stopped using pesticides they would assure a cataclysmic infestation that would lead to the quarantining of California produce, costing 132,000 jobs and $13.4 billion in lost trade.
The infestation was real enough. It was ended by heavy spraying. It is still not known if ecoterrorists were behind it, but the panic it engendered shows that “the Breeders” were flirting with a powerful weapon.
The history and future of insects as weapons are explored in my new book, Six-Legged Soldiers. As an entomologist, I was initially interested in how human beings have conscripted insects and twisted science for use in war, terrorism and torture. It soon became apparent that the weaponisation of insects was not some quirky military footnote but a recurring theme in human strife, and quite possibly the next chapter in modern conflicts.
Insects are one of the cheapest and most destructive weapons available to terrorists today, and one of the most widely ignored: they are easy to sneak across borders, reproduce quickly and can spread disease and destroy crops with devastating speed.
A great strategic lesson of 9/11 has been overlooked. Terrorists need only a little ingenuity, not sophisticated weapons, to cause enormous damage. Armed only with box-cutters, terrorists hijacked aircraft and brought down the World Trade Centre. Insects are the box-cutters of biological warfare - cheap, simple and wickedly effective.
Am I being an alarmist? I wish I knew. But I do know that few people have an inkling of how insects can - and have - been used to inflict human suffering and economic destruction. And I know that government officials admit that entomological attacks are, “not something that is yet on our radar”. So my goal in Six-Legged Soldiers is to find a measured concern that lies between complacency and panic.
Yet insects have shaped human history. In the 14th century, 75million people succumbed to flea-borne bubonic plague. But few people realise that the Black Death arrived in Europe after the Mongols catapulted flea-ridden corpses into the port of Kaffa. People fled, carrying bacteria, rats and fleas throughout the Mediterranean.
And it was lice, not enemy armies, that nearly broke the back of the Soviet Union when typhus made 30million people ill and killed 5million after the First World War.
Military strategists have seen the potential for warfare in all this. In the Second World War, the French and Germans pursued the mass production and dispersal of Colorado beetles to destroy enemy food supplies, and the Japanese military killed more than 400,000 Chinese by dropping plague-infected fleas and cholera-coated flies.
During the Cold War, the US military planned to produce 100million yellow fever-infected mosquitoes a month, and produced an “entomological warfare target analysis” of vulnerable sites in the Soviet Union and its allies' terrotories. The dispersal and biting capacity of (uninfected) mosquitoes was tested by secretly dropping them over US cities.
America believed that insect-borne diseases were the bane only of underdeveloped nations until the summer of 1999, when West Nile virus arrived. A natural experiment in entomological warfare unfolded. over the next seven years, the technological might of the US could not stop mosquitoes carrying the disease across the nation, infecting nearly 7,000 people and killing 654.
Many insect-borne pathogens could afflict Western nations. But given the losing battle against West Nile virus, the greatest concern is its African cousin, Rift Valley fever. Originally discovered in 1931, this viral disease caused miscarriages in livestock while young animals suffered 10 to 70 per cent mortality rates. Mosquitoes spread the virus from Kenya. In 1997 a virulent strain appeared, able to infect the human nervous system. About 200,000 Egyptians fell ill, of whom 2,000 lost their sight and 598 died of encephalitis. Every region of the US has a mosquito species that is capable of carrying the disease.
Nor would it be difficult to introduce. According to biodefence experts, a terrorist with $100 worth of supplies, simple instructions and a plane ticket could introduce Rift Valley fever to the US or another target country with almost no chance of being caught. Western societies are understandably worried about disease, and terrorists would relish the opportunity to introduce deadly pathogens. But they are aware that we take our wealth as seriously as our health. The World Trade Centre was an icon of US economic prosperity. And agriculture accounts for a trillion dollars in economic activity as well as one in every six jobs in the US.
An entomological attack would not empty America's larders completely but it could go a long way to emptying its wallets.
In economic terms, the 9/11 attacks resulted in direct losses of $27.2 billion. The Asian longhorned beetle, which arrived in 1996, with the emerald ash borer, found in 2002, together have the potential to destroy more than $700 billion worth of forests, according to the US Department of Agriculture.
What would be the cost of an insect-borne disease? If it destroyed enough orchards to cut the sale of orange juice by 50 per cent for five years, the US economy would lose $9.5 billion - approximately the cost of building the World Trade Centre from scratch.
Stacking a nation's defences along its borders is a strategic error. The better model is that of public health. Rather than hoping to stop every sick traveller entering a country, a wise government would stockpile vaccines, train health professionals and educate the public.
The best “homeland defence” is flourishing human and agricultural health systems that can detect and deal with whatever comes in. Such an infrastructure would pay for itself. Even without terrorists, new diseases and insect pests will continue to arrive.
Western societies tend to think in terms of the short-term spectacle and heroic saviours of Hollywood action movies. Our disconnection from the natural world makes us believe that risk and benefit unfold at a blistering pace. For a terrorist group with patience, a slow-motion disaster in ecological time would be a perfect tactic against an enemy that thinks in terms of days or months, but would suffer across the generations.
Jeffrey A. Lockwood, the author of Six-Legged Soldiers: Using Insects as Weapons of War (OUP). Educated as an entomologist, he is a professor of philosophy and creative writing at the University of Wyoming.