Why we need flies: For chocolates, mangoes and more

We revile flies, because they buzz around in filthy areas – sewage plants, garbage dumps, rotting carcasses, dung heaps, landfills full of muck and try to crawl up our noses or into our eyes. And yes, they do spread diseases. (The mosquito is technically a fly). But if they didn’t inhabit and dine in these disgusting places, we – and our planet – would be neck deep in feces because flies turn this muck, rotting carcasses, decaying leaves and feces into nutritious soil. Long ago, nurses attending dreadfully mangled soldiers on the battlefield discovered to their surprise that those whose injuries were infested with the maggots (larvae) of blowflies, had a much less chance of their wounds becoming infected and turning gangrenous. And that was because the maggots were feasting off the dead – often hideously burnt – tissue and leaving the healthy tissue around it intact. Surgeons are doing this now to treat gangrenous wounds and burns without recourse to antibiotics.

Blowfly maggots are also used in forensics – to indicate the time of death of

say a murder victim – by the stage of development they are in when the body is examined – and whether the victim had used or been given narcotics. Blowflies can smell a dead body from one mile away, will wing over and the females will promptly lay their eggs on the carcass. Lest we turn into blowfly fans now, we must also be aware that blowflies spread a host of very unpleasant diseases, both in humans and animals, some thanks to that disgusting habit that flies have of vomiting out their food before sucking it up again.

Worldwide, there are over 160,000 species of flies, the most well-known, and probably unpopular, being the housefly. They are remarkably engineered insects: equipped with moveable heads, massive bulging compound eyes, which can see in slow motion enabling them to easily escape the descending flyswatter, two strong fastback, cellophane-like wings, (flies are known as Diptera) mouths that can suck, lap and pierce, legs that have claws at their ends, enabling them to grip the surface they land on. Two stubby extensions behind their wings – which evolved from their hindwings, known as halteres, work as gyroscopes to help them orient and balance in flight, vibrating along with the wings and enabling them conduct those fantastic flying maneuvers such as landing upside down on the ceiling after doing a somersault in mid-air. (None of our hi-tech planes can do that!)

Some flies are iridescently gorgeous, one species of solider fly from Australia is a beautiful shimmering mix of blue and purple, another with a bright golden abdomen has been named Plinthina beyoncae after the singer Beyonce. Some species when in love will woo their partners with edible gifts (chocolates?!) while others will dance for them.

Robber or assassin flies – of which there are around 7,000 species – are stockily built, powerful flies that ambush their prey on the wing. Fruit flies, aka banana flies, with their orange eyes, are attracted to rotting fruit and, thanks to their short lifespans and simple genetics, have been used for biological and genetic research. That part they were the first animal to be launched into space, way back in 1947.

Flies are probably no one’s favourite insect but do keep an eye out for hoverflies (aka flower flies) and you might just be astonished! Some are disguised like small bees and wasps, striped black and yellow, with large polished eyes, but what’s stunning about them is the way they fly. They can suspend themselves perfectly still, in mid-air for many long seconds, dart up and down and right and left in a trice and then hang suspended again, their wings a blur. There are about 6,000 species spread worldwide, and no they do not bite or sting. I’ve spent hours trying to photograph them on the wing and while they allow you to focus properly, the moment you press the shutter, they invariably vanish! Use a very fast shutter speed (in continuous mode) or stroboscopic flash and you may be able to discern the way their cellophane wings twist and turn during each wingbeat. Scientists investigating insect flight, used scaled-up models of hoverflies and made them ‘fly’ in oil just to figure out how insects were able to generate enough lift for flight and discovered the vortices rolling off their wings like little tornadoes providing lift and thrust. Which avionics engineer would have thought of that?