Fantastic Mr Fly

Often seen as a major nuisance and hazard to public health, the common housefly is a ubiquitous insect—so much so that their presence is simply taken for granted. Yet, it packs a mighty punch within its diminutive frame. We take a closer look at this constant co-inhabitant of our homes, gardens and lives.

I was reading The Fly—one of William Blake’s most lyrical poems and included in his famous literary work Songs of Experience, on an early morning in August. As I started to read, ‘Little Fly / Thy summer’s play …’, on a warm and humid day, I became well aware of the contrasting experience I was having with the annoyingly large swarm of houseflies around me. I had barely reached the fourth line, ‘My thoughtless hand / Has brush’d away,’ when I was forced to consider how someone could find inspiration in something so annoying. Trying to see what the poet had seen and the rest of us had missed, I set about on my personal quest of decoding the fly.

Flying health hazards

The housefly is ugly in appearance and dirty in its habits, with a proven track record of carrying deadly pathogens, and millions of microorganisms, both inside and outside its body. On the paws of its six feet, within the mouth parts, excreta, saliva and on the wings, a single fly can carry a diversity of bacteria, protozoa, viruses, fungi. The common housefly has been known to spread cholera, typhoid, dysentery, tuberculosis and several other parasitic worms. It can thus be safely dubbed as a flying public health hazard.

But astonishingly, it grooms it body parts – eyes, wings, and abdomen – meticulously with its legs, dusting off any accumulated particles. I noticed one fly grooming itself on my bath towel, seemingly oblivious of the surroundings, including me. What is even more astonishing is that the housefly itself is immune to the pathogens it carries, something that scientists are learning and hoping to replicate in humans by decoding the fly’s DNA. Amazingly, the fly can even rest upside down on our ceilings, quite out of our reach. Just like geckos, even these insects can stick their ‘paws’ on pretty much any surface, allowing them to walk vertically or upside down.

The housefly prefers human-dominated areas, be it an urban setting, a rural village, or even a small, isolated settlement. Thus, it is found almost all over the world. But the warm and moist climate in the tropical and sub-tropical zones is the most fertile ground for the fly. Because of their large scale dispersal, the fly is fit to be called a pest of universal and cosmopolitan nature. Human population profusely generates garbage and waste of all sorts, and these are the perfect residential complexes for the flies. So in fact, it is we who are responsible for providing the perfect environment to the flies to thrive and multiply, and they are simply reciprocating our favour. This dangerous liaison between us and the flies is one which appears to be very difficult to disengage from, as the flies have developed immunity to several of our insecticides by now. They are more than happy to visit our homes to feast on our food, while leaving their footprints, excreta and saliva all over them.

Photo: Wikimedia Commons

Photo: Wikimedia Commons

Packed with features

Scientifically, the housefly is called ‘Musca domestica’ and is placed under the insect order Diptera, the group of all two-winged insects in the world, encompassing about 2,40,000 species. If you study the lifestyle of flies, you will realise that there are some amazing facts hidden from common knowledge. The housefly is about 8-10 mm long, has a grey thorax with four longitudinal dark bands on its back, a hairy body, and a pair of blood-red compound eyes. Each of these eyes is actually made up of thousands of tiny lenses; they give the flies a really wide field of vision and a good depth of perception. They are also highly efficient at detecting polarisation of light and colour spectrum unseen by our eyes. Because of this acute vision, flies can detect movement extremely quickly, making it difficult for us to swat them. Male houseflies are slightly smaller in size compared to females, but are endowed with larger eyes. In females, the eyes are located some distance apart, separated by a proper dividing mark in between them. This is the easiest way of differentiating between male and female flies.

The lifespan of the adult is short, ranging between 15 to 30 days and dependant on environmental factors. Females lay eggs in clusters, about 75 to 150 in one go and account for 8,000 to 9,000 eggs in a lifetime. The eggs are tiny, about 1.2mm in size and hatch within 24 hours into the larval stage, where they are called maggots. The maggots transform into the pupa stage and the adult emerges from the pupa, completing the entire metamorphosis in 10-12 days. Females are ready to mate within 36 hours. Mating rituals last only for a few seconds and are mostly airborne, but a couple sometimes alights onto a surface as well.

The wafer-thin, transparent wings have longitudinal, straight veins to impart strength and stiffness while in flight. The inner margin of the wing has a distinct loop, a signature of a housefly wing. This loop can even be noticed with the naked eye.

An extremely agile aerial performer, the housefly can change directions at will, this being another reason why it is difficult to swat a fly. To cope with the stress and strains generated during these fantastic flights, it has developed halters – a set of stunted wings set on the fly’s back. The halters impart aerodynamic stability during high speed flights which are often coupled with sharp twists and turns, preventing the fly from tumbling over. I am sure that the housefly would be under tremendous G-force as it manoeuvres through the air with ease, a lesson our aeronautical engineers are yet to learn.

Photo: Yuvaraj Gurjar

Photo: Yuvaraj Gurjar

Outside the house

The housefly is most certainly considered repulsive in appearance and spirit. But some of its sister species, like the Common green bottle fly (Lucilia sericata), which bears a brilliant metallic green colour and is like a gem in appearance, are very attractive looking. The Common green bottle fly also has a near metropolitan distribution, but generally desists from making an entry into houses. These flies can be usually seen basking on plants in the morning sun. The maggots of this fly species are of use in the medicinal world, in healing wounds. They eat away the infected and dead tissue from the wounds and help in the regeneration of new healthy tissue with their secretion, thus healing the wound faster. This is known as ‘maggot therapy’.

Some maggots are even used in the production of special varieties of cheese in parts of Italy. Forensic science has also found out a way to make use of maggots; by studying the maggots present in a corpse one can determine the time that has elapsed after death. The maggots allow the dead to tell their own story!

Another commonly seen fly is the Common blue bottle fly (Calliphora vomitoria), from the group called blow flies. These flies are larger than our houseflies and display a high affinity towards foul-smelling and rotting things, including flowers emitting strong odours. As a result they end up pollinating quite a few flowers. Fortunately, they spare our homes and are generally found in open spaces. Can a fly also give clues on how to build hearing aids? Ormia ochracea, a nocturnal fly endowed with highly acute sense of hearing, has done just that. Based on the structure of the fly’s ‘ears’, which are capable of catching the faintest of sound vibrations created from far away and pinpointing the exact location, scientists have developed a hearing aid, only 2mm in length. This process of designing machines based on a natural subject is called biomimicry.

Despite all that we know about houseflies, they are often not considered to be as much of a menace as a mosquito, simply because they do not bite. The truth is that houseflies actually lack any sort of teeth or beak required to bite. They instead have a spongy mouth part, which extends out to eat any liquid or semi-liquid food.

So why do they keep on landing on our body if they do not intend to (or cannot) bite? It is only to supplement their diet with salt intake present from in our sweat.

Despite the swarming flies, I somehow managed to finish the poem, ‘Then am I / A happy fly, / If I live / Or if I die,’ still amazed at how a fly could have inspired someone to write such a beautiful philosophical poem.


Cover Photo: Yuvaraj Gurjar

Read also: Junglimericks: In the Crazy Wilds of India

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About the Author /

A Civil Engineering graduate from BIT, Ranchi, Prabhat Kumar retired from Coal India in 2005, as Chief General Manager (environment). Currently serving as visiting faculty in engineering colleges at Ranchi, he is a keen nature photographer and regularly contributes articles to magazines.

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