The unexpected life of the world’s most successful insects
By Jonathan Balcombe
For ancient thinkers, the life of a fly had cryptic origins. With little knowledge of how flies metamorphose from larvae to adults, some classical philosophers believed that insects emerged by “spontaneous generation” of fires, rotten meat, mucilage and other organic wastes; life springs from non-living matter.
Winged insects such as these did not need companions or parentage, philosophers theorized, because they did not reproduce. Iota by iota, the debris was thought to transmogrify into flies. And so, therefore, something of the inanimate realm still clung to them; an unresponsive state, the feeling that flies were less beings than things. Whatever stain of animacy danced inside a fly, it was imperfectly drawn from its humble genesis in the mud or smoldering trash.
Naturalists have since detailed the true life cycle of the fly (its perpetual circuit: egg, fly, chrysalis, midge), but the notion that flies are tiny automatons persists. Flies are said to buzz or buzz, sounds that evoke machines. En masse, we see them as a “cloud,” a presence as fickle (and sometimes as powerful) as the weather. Watching flies spin around a light bulb, like planets on an invisible orrerie, the balance of their movement might strike an idle mind as seemingly predefined, with each flight path being produced by a still unrecognized kinetic law, instead. to be – as is the alternative – the result of a fly’s instant decision-making, a trajectory driven by intention.
So it’s kind of a revelation, then, to learn through Jonathan Balcombe’s latest book, “Super Fly: The Unexpected Lives of the World’s Most Successful Insects,” that far from operating on autopilot. , flies exhibit socially demanding, idiosyncratic behavior and sensitivities to stimuli that are no different from our own.
Courtship, for example, offers a remarkable panorama of romantic tension and strategy. There are flies that present potential mates with edible gifts, wrapped in silk bundles that scientists call “nuptial balloons.” Some flies emit an aphrodisiac scent, dance or sing for attention (although they do this by vibrating their wings, not vocally). The flies kiss each other. Bone-skipper flies, competing for territory and sexual primacy, charge at lightning speed, banging their heads like bighorn rams do in the Rockies. Females of a different species inflate their abdomens to mimic pregnancy; a semblance of fertility, exciting for the men, which Balcombe compares to “a commotion of flies.” Copulating tsetse flies shake and squeeze their bodies in a synchronous pattern that is thought to be a kind of inner dialogue; steal dirty talk.
The smallest fly is the size of a pepper flake. Among the larger ones is the thieving fly, which can grow to nearly three inches and is capable of taking down a hummingbird, although its brain weighs barely a milligram. Flies have evolved to occupy some of the most extreme environments on the planet. One type lives in puddles of crude oil, another in the excretory organs of a land crab. Alkaline flies scurry across the top of a lake, creating wavelets that then engulf them, enveloping each fly in a silvery bubble that allows it to dive and feast on the algae below.
Among the flies that make their habitat on other animals – parasitizing the skin or body tissues, feeding on blood – the rarest are those linked to endangered animals. Today the rhino-stomach botfly is blinking, having fewer rhino stomachs to colonize, as rhino numbers drop. Against the mosquito, which is also part of the Diptera fly family. The mosquito enjoys an expanding area of human skin. As Balcombe notes, these flesh flies and others have access to approximately 4,600 square miles of skin surface in the world; and as our species grows, so do their profusions.
“Super Fly” belongs to a sub-genre of animal literature which frequently sees recourse to titles which begin: “The secret life of _____” (bees, cows, wolves). But Balcombe’s book does more than uncover surprising facts about flies. The effect of being immersed in this miniature world is a disturbing feeling of double vision. Where once flies could have represented boredom or torment, “Super Fly” reveals an existence that is not necessarily simpler because it is simply smaller.
Hearing that fruit flies suffer from insomnia may well inspire us to reimagine what this point does, dizzyingly circling the ceiling. Or think. Is a fly a torment in itself, desperate to sleep? Astonishing, that this complexity is playing out right under our noses (or above our heads). What else do we lack?