Tuesday , 13 November 2018
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Flies and their love for humans

Maneka Sanjay Gandhi

 

I checked into an ayurvedic centre in Haryana for a week. Clean, spartan and strict, it was the ideal place for me…. except for the flies. I was covered with oil or mud for the better part of the day and showered three times but it seemed to me that I had become a target for all the flies of the district. No one else seemed to have a problem. But walking, sleeping, being massaged or eating, I was brushing away the House Fly (Musca domestica), and its more ubiquitous cousin the Bush Fly (Musca Vetutissima).

Why do flies sit on humans? It is so energy expensive for them. They are brushed away a thousand times, swatted, hurt, killed. Why don’t they sit on animals, or furniture? (They do sit on animals, but only those that are hurt and cannot defend themselves.) Since the common housefly doesn’t have any interest in sucking blood, (feeding on open wounds is a different story), you think they’d fly away from humans. After all, we’re a lot larger and more intimidating swatters.

The fly has a very soft, fleshy, sponge-like mouth and when it lands on you and touches your skin, it won’t bite; it will suck up secretions on the skin.  It is interested in sweat, proteins, carbohydrates, salts, sugars and other chemicals and pieces of dead skin that keep flaking off. This type of fly also gets its nutrients from sitting around the eyes of livestock. It is hard to get it from anywhere else on hairy animals, which is also why they land more often on human skin which is comparatively less hairy.

Here are some reasons why they land on humans

l They are attracted to carbon dioxide which human beings breathe out.

l They are attracted to the heat of the warm body, to sweat and salt, and the more the person sweats the more flies they attract.

l Flies feed on dead cells and open wounds.

l Oil is an important food for flies. Oily hair is an attractant.

l Less hairy skin gives the fly spaces to vomit. A fly vomits on solid food to liquefy it. The house flies taste with their feet so if there is food on the skin, and space to liquefy it, they will land there.

l Some body odours are more attractive to flies than others. This is apart from the quantity of carbon dioxide that is emitted.

Houseflies are scavengers. The human body, like some of their favourite food sources — faeces, food and rotting flesh — radiates a sense of warmth and nourishment. With a voracious appetite, aided by an excellent sense of smell and a pair of complex eyes that covers half its head, the fly lands on us because it is  constantly on the hunt for a warm place to eat, defecate, vomit and lay eggs.

In order to make the area in and around your home a “no fly” zone take basic preventative measures. If you have a dog make sure you do not leave its faeces out in the open, as dog faeces serves as both buffet and egg depository. Don’t leave food out for too long, pay special attention to kitchen utensils and surfaces, empty your garbage cans regularly and keep an eye out for organic rotting matter. Don’t leave food in pet bowls after they have eaten. Wipe down trash cans from the outside as well. Net all the windows and shut the doors. Check for cracks and holes (particularly around window screens) that they might be using. Unhygienic rubbish tips are a prime fly-breeding site, but if garbage is covered by a layer of soil, preferably daily, this can be avoided.

But why are certain people singled out?

Could it be the scent in the soap or shampoo? Apparently, sweet fruity smells attract flies because they like sugar. Maybe your skin, mouth and nostrils are moister than others. It is also claimed that flies and gnats migrate to the taller persons in a group. You don’t have to sweat a lot – just more so than the rest of the people in your house to make it more likely for them to land on you.

Fruit flies are slightly smaller than the common house fly. They are not interested in human smells but in yeast, so they are attracted to things that are fermenting and  can ferment, like sugar, fruit and, of course, actual yeast. So, if you drink alcohol and hang around with people who don’t, or if you use grooming products with alcohol in them, you will attract fruit flies. Don’t eat fruit outside? Switch your soap if it is fruit smelling. But apart from swatting and waiting for winter, there is little you can do.

Blowflies, also known as bottle flies, have metallic green or blue bodies, are large, and make a buzzing sound when they come near. They are really a nuisance for me because they lay their eggs on animals, and my hospitals get thousands of animal patients every week suffering from maggot infestation. There are other flies as well: the Drain fly found in sewage beds whose wings are densely covered in hair and held tent–like over the body when at rest; the Flesh Fly, whose three-striped body looks like a chequer board, lays its eggs on decaying meat or fish or animal flesh.

Swatting a fly is so difficult. Their eyes allow them to see all around and they have a sixth sense about danger. According to the California Institute of Technology flies fly within 100 milliseconds of recognizing a threat.

Flies have been around since before humans. In the Biblical plague of Egypt, flies represent death and decay. The Philistine God Beelzebub’s name, (often equated with Satan), means Lord of the Flies. In Greek mythology Zeus sent a fly to bite Pegasus, the winged horse, causing his rider Bellerophon to fall back to earth when he was attempting to fly to Mount Olympus the home of the gods. In the Red Indian Navajo religion Big Fly is an important spirit.

Many scientists have tried to find out how to use flies constructively. Suggestions range from mass rearing them and using them on animal manure garbage dumps. (Flies are recyclers. They eat scraps and then excrete and turn it into a substance plants can use). Or harvesting their maggots and feeding them to animals. Both these ideas seem insane to me.

Ogden Nash’s poem sums up our irritation with this being “God in His wisdom made the fly / And then forgot to tell us why.” Perhaps to keep human populations down by spreading diseases that range from dysentery to typhoid and cholera. During the Second World War the Japanese, under Shiro Ishii, used special Yagi bombs on China. The bombs contained flies coated with cholera bacteria. The bombs thrown in Baoshan in 1942 and Shandong in 1943 killed over 4 lakh people.

Anyway now that I am back, my fly demons seem to have lessened. So maybe it was the oil.

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