House flies are the commonest and most familiar of all insects which live close to man. In India, they occur in abundance all the year round. The majority of house frequenting flies in India are non- biting. House flies should be regarded as a sign of insanitation, and their number is index of that insanitation.
The common housefly (domestic) is mouse gray in color. The body is divided in to a head, thorax and abdomen. The house fly undergoes a complete metamorphosis with four stages in its life cycle: egg, larva, pupa and adult. Flies do not generally live longer than 15 days in summer and 35 days during winter.
The habits of housefly make it eminently suited for the spread of disease. The most important breeding places of flies in order of importance are (a) fresh horse manure (b) human excreta (c) manure of other animals (d) garbage (e) decaying fruits and vegetables (f) rubbish dumps containing organic matter and (g) ground where liquid wastes are spilled.
The housefly does not bite. It is attracted to food by its sense of smell. It cannot eat solid food it vomits on solid food to make a solution of it and sucks in a liquid state.
Adult flies delight in sputum, faces, discharges from wounds and open sores. The fly is a restless insect and moves back and forth between food and filth. This helps in the spread of infection mechanically. As the fly vomits- frequently, the 'vomit drop' is often a culture of disease agents. Flies have a tendency to rest on vertical surfaces and hanging objects.
They have a tendency to fly towards light. Normally houseflies remain close to their breeding places, but they disperse frequently up to 4 miles, and sometimes' even longer from the point of their origin.
Transmission of Disease:
Flies are potential factors of many diseases:
typhoid and paratyphoid fevers, diarrheas and dysenteries, cholera, conjunctivitis etc. and in fact most diseases that can be spread by mechanical contamination;
Flies transmit disease in the following ways:
(i) Mecbnica Transmission:
Houseflies are exceptionally efficient mechanical spreaders of disease. They transport microorganisms on their feet and hairy legs. Therefore the houseflies are called ' porters of infection".
(ii) Vomit Drop:
The vomit drop is a rich bacterial culture and by its habit of frequent vomiting, the housefly infects food and thereby transmits disease.
The excrement of housefly has been found to contain numerous micro organisms as well as cysts and ova of intestinal parasites. By its habit of constant defecation, the housefly spreads these diseases.
Fly Control Measures:
The elimination of the breeding places and overall improvement in the environmental sanitation on a community-wide basis is the best way to control houseflies. A’ clean house with clean surroundings is the best answer to the fly problem.
(ii) Insecticidal Control:
Insecticides such as, D.D.T. B. H. C. Parricides, Baits etc. should be applied to control the houseflies. D.D.T. or B.H.C. may be applied indoors or outdoors using hand or power sprayers. But they produce only a temporary effect on adult fly populations; consequently, repeated applications are necessary. This will be more effective if used for the treatment of fly breeding places. Special care should be taken to prevent contamination of food or water during spraying operations, However, it may be stated that insecticides, at best, only a supplement, but not a substitute for sanitation.
(iii) Fly Papers:
In certain cases sticky fly papers are used to control the house flies. These papers can be easily made by mixing 2 lbs of resin and one pint of castor oil which should be heated together until the mixture- resembles molasses. This should, while hot, be. Smeared on paper by using an ordinary paint brush. Although a slight reduction of flies may occur, no lasting benefits will result from the use of fly papers.
(iv) Protection against flies:
Screening of houses, food markets, restaurants and all other similar establishments will give considerable relief from houseflies. But this, is expensive for general use,
(v) Health Education:
It is difficult to achieve fly control without the willing co-operation of the people. It is only through health education that a fly consciousness’ can be created among the people and they can be motivated with a desire to get rid of flies permanently.