Everyman's enemy: the housefly (1955) Pt. 1 of 2

[Music] Flies mean different things to different people to the angler there are imitations in feather and silk of the natural flies which occur by lake or river they are designed to lure the unsuspecting trout into taking them for the real thing but to most of us flies are a nauseating menace to be shaken off at all costs there are in this country more than 5,000 species of flies but fortunately only a few of them can justifiably be regarded as pests the the housefly and its close relatives the blowflies are probably the best known of all they are familiar to everyone in Town and Country and are notorious for their unpleasant habits their liking for human food brings them forcibly to our attention during the warmer months of the year shopkeepers and others handling food are constantly worried by flies which may contaminate the Commodities they handle in Canning and other food factories steps must be taken to prevent flies and other insects from having access to the product eyes cannot be tolerated in hospitals even in small numbers apart from being objectionable in themselves they can be responsible for cross infection and the contamination of sterilized instruments and Equipment the housefly can be distinguished fairly easily from its relatives the Lesser housefly which is noticeably smaller the stable fly which has a sharp prosis for piercing the skin and the green bottlefly which has a characteristic color to breed successfully house flies require decaying organic matter which is both warm and reasonably moist refuse tips and pigies are examples of the very large number of situations which often meet these requirements batches of as many as 150 eggs are laid by the female flies and one female may lay four or five batches on separate occasions during her life the young LA emerg from the eggs sometimes only a few hours after they were laid and nearly always within 2 days they soon borrow away from the light into the food medium where they feed almost constantly and grow rapidly their speed of development is faster at higher temperatures at 60° Fen they reach maturity in about 2 or 3 weeks whereas at 7 to7 they can do so in about 6 to 8 days when the L are full grown they tend to migrate to cooler places before they enter the next stage of their development the pupa or chrysalis large numbers of pupy can sometimes be found in the soil around a refuge tip loose Earth provides the insects with suitable conditions in which to pupate the duration of the pupil stage before the adult emerges depends on temperature and can vary from 2 to 3 Days To several weeks when the remarkable change from grub to fly has occurred inside the pupil case the case splits and the adult insect pushes its way out to assist it in doing so a sack on its head inflates this sack is only a temporary structure and deflates soon after the fly has emerged the wings of a newly emerged fly take several minutes to unfold and dry before the insect can take flight one pair of flies could have as many as 800 direct Offspring and when in favorable conditions the generations of adult fly follow each other at intervals of about a fortnight it is not difficult to understand why large populations of flies seem to develop suddenly it has been estimated that if the number of flies which in theory could be descended from a single pair during one season were to be realized their bodies would cover the entire surface of the Earth to a depth of 47 ft apart from being very able Flyers house flies can walk about easily on most types of surface the pads of a fly's foot have powerful adhesive properties which enable the insect to walk on window panes and ceilings the most prominent features of a F's head are its compound eyes and the mouth Parts which are adapted for licking and sucking when flies feed on solid food such as sugar they first regurgitate liquid onto it and then suck up the food in solution the habits of the housefly make it dangerous as a potential carrier of disease the fact that bacteria can be carried by a fly may be demonstrated in the laboratory by allowing it to walk over a culture plate the bacterial colonies which develop after incubation can be seen under a microscope along the track left by the fly bacteria can also be carried on other parts of the fly and when a fly has imbibed food containing bacteria the bacteria can pass unharmed through its body the bacteria which can be carried by flies opportunities permitting include those which are responsible for various diseases of man such as typhoid dentry and summer diarrhea there is also evidence to suggest that flies may play a part in the transmission of polio the danger of flies acting as carriers of disease emphasizes the need for their principal breeding grounds to be discovered and for control measures to be prce practiced refuse from private and Industrial premises is a frequent source of trouble but good collection and Disposal methods prevent a serious fly nuisance developing battered dust bins with badly fitting Lids allow easy access to flies on the other hand bins which are in sound condition largely prevent flies from reaching refu awaiting collection