Book Review: The Secret Life of Flies

Flies are everywhere. They're in our homes, beneath of the streets of our cities, and even in the frozen depths of lakes. There are some 17 million flies for each and every one of us on the planet and some 24 species that feed on wombat dung alone. And yet, despite their great number and great geographic spread, the world of the fly is relatively unknown. There are an estimated 400,000 - 800,000 fly species in existence but only 160,000 of those have been recorded to date.

The Secret Life of Flies

Luckily, the fly has a wonderful champion in Dr Erica McAlister, Senior Curator at the Natural History Museum in London who shines a light on these extraordinary creatures in her terrific book, The Secret Life of Flies. The book takes readers from the archives of the Natural History Museum to mountains in Peru via drains and cow pats and introduces us to wonderful creatures including tipsy vinegar flies, bat flies swimming through the fur of their hosts and midges that can survive temperatures of below -62 degrees celsius.

With an enthusiasm and a wonderful knack for story-telling, McAlistair has crafted a book that is a delightful ramble through the world of flies. But make no mistake, McAlistair is on a serious mission to tackle the common misconception that flies are simply disease-carrying nuisances. Throughout the book, she employs her great knowledge and communication skills to reveal just how important these creatures are.

The book is structured so that each chapter details one of the roles that flies have evolved to carry out. The first chapter explores the pollinators such as the biting midge family, known as the 'No See Ums', the only pollinators of the cacao plant fruit. Other chapters introduce us to the detritivores, who help rid the world of rotting vegetation, the carrion-feeding necrophages, the predators and the sanguivores (bloodsuckers) which include the much-maligned mosquito. 

A world without flies would indeed be a dreary and a filthy one. For without flies, we would have no chocolate, mangoes, chilli peppers or onions; and, perhaps more alarmingly, would be knee deep in dead bodies and, how to put this delicately?, well, in s**t. 

And that's before we consider the important role that flies play in medicine, both in aiding treatment and in helping disease prevention. Ghengis Khan was said to have a caravan full of maggots, which he used to treat the gangrenous wounds of his soldiers. In Victorian times, consumptives would sit in so-called maggotoriums beside troughs of maggots to inhale healing fumes. Even today, they are used in medicine to remove rotten tissues and help heal the wound by secreting an antiseptic compound. Marsh flies are used in the field of biological control to kill snails which are hosts to infections such as bilharzia - a disease with an infection rate in Africa second only to malaria. And flies play an important role in research. Vinegar flies tipsy on fermenting fruits and yeasts are used to understand alcoholism:

“We have used their love of a wee tipple to learn more about human behaviour and gene expression. When the adult flies commence drinking they become clumsy and start lolling around, falling onto their backs. What’s more, as they drink more they become more amorous and far less able to pick a suitable mate.”

For decades, flies have been helpful to medical examiners trying to establish a reliable time of death, and these days, researchers are looking at how maggots might play a role in the development of new antibiotics. Certain fungi-loving flies can help detect anything from undiagnosed moisture issues in a house to truffles growing underground. 

It's not just the functional value of flies that should make us think twice about wielding a fly swat, for as the book makes clear, 'no other group is more adaptive, crazy or more ingenious in their morphology and general bad-ass behaviour'There are flies that can eat boot polish and emulsion paint; others that can survive 5,700 feet down at the bottom of Lake Baikal; species that swallow air and pump it through their own bodies to inflate their eyes and horseflies that can get up to speeds of 90 mph. And, I never thought that I would find beauty in a fly, but I defy anyone not to admire the devilishly handsome hairy drain fly or the adorable round-faced Cuterebra Emasculator. 

McAlister set out to write a book to dispel common misconceptions about flies. It certainly achieves that by making a strong case for the value and importance of flies but I believe that it does so much more. It describes a world so extraordinary and captivating that it makes us thirst to learn more about these incredible but much-maligned creatures - and that's no mean feat.

My thanks to the Natural History Museum publishing team for a review copy of the book.