George Hurlstone Hardy

“ GENERAL LIFE HISTORY Whereas the blue-bottle rarely enters the dwellings of mankind, except gravid females led by the sense of smell in search of fish, or flesh meat, and (less eagerly) sweets, both species of house-fly and both sexes seem to delight in the mere odour of humanity; breeding females will seek the larder and the dust-bin, but others will very provokingly pervade all quarters. Although avoiding a dark or deeply shaded room, the house-fly seems to like partial shade ”

“ These creatures may well be imagined to have developed out of some primæval species by reason of the increase of mankind upon this planet. The mere presence of the house-fly denotes some nuisance more or less remote; the local density of the brood indicates the degree and the proximity of unsanitary conditions. Under present circumstances the visitation of the house-fly is Nature's intimation that peril of a very insidious character is about. Very properly, Nature's messenger will not be denied, and pertinaciously manifests herself to us indoors! ”

“ The general fate of maggots living on the floor of well-kept horse-boxes is to end their lives drowned in the drains to which they descend, when or before they pupate.
In these days of motor-cars and fewer horses the horticulturist everywhere is eager to buy good stuff; now stable manure to be good must be fresh and free from the garbage with which stable men wantonly corrupt the same, instead of consigning such extraneous refuse to a proper separate dust-bin for collection and cremation. ”

“ In the matter of food which becomes fly-infected after having been cooked, or of food like milk, butter, and fruit, which are consumed raw, it should be known that a single pathogenic germ of ultra-microscopic dimensions, having obtained lodgment in the body, may there multiply and originate a fatal disease. On the other hand, raw meat which has been infected may, after the bacteria have been all killed by cooking, contain excreted poison in deleterious quantity. ”

“ However, the younger flies seem to feel no such restrictive influence, for, as soon as they have become fit and the weather suits, they show an inclination to fly high and thus may travel to very remote places. It is just the same with peacock, red admiral, and tortoise-shell butterflies, which I have often reared and released for adding to the interest and beauty of a flower garden. In sunny weather many or most will soon wander never to return; those which have remained a few days continue residence close round about, especially if nettles, the food plant, grow in the neighbourhood. ”

“ The presence of the house-fly in our dwellings is often submitted to as an irritating but an inevitable nuisance; yet very certain remedial measures would almost exterminate the creature, which is a dangerous and filthy peril. To many people it will seem a most incredible exaggeration when told that it is really worse than any one of the less common creatures universally regarded with horror and disgust as pestiferous vermin. ”

“ It has been commonly but not truly said that the principal breeding places of the house-fly are the mews and the farmyards where manure is allowed to accumulate; the house-fly has a preference for horse dung before cow dung, which is preferred by some other kinds of flies; however, near towns, the domestic dust-bins, heaps of market garbage, and deposits of town refuse give rise to a worse plague of house-flies than stables. All these flies deposit batches of white eggs, and are careful to place them as much as possible in crevices and shielded from exposure to strong light, or from draughts. ”

“ The wing pattern is the readiest guide for distinguishing the lesser house-fly, both male and female. The males of the hairy (almost bristly) raven-fly also indulge in the dancing habit, but still more so do those of the latrine-fly, Fannia scalaris, which may be distinguished by its uniformly ashy-grey abdomen.
These common co-inhabitants of our dwellings vary in size according to their nourishment when in the larval stage (maggots) ; after the perfect insect emerges from the puparium, it swells out and fattens, but does not grow in the real sense of the word. ”

“ MYIASIS AND THE ŒSTRIDÆ The family of the Œstridæ is the most curious and horrific of all the different tribes of flies; it is very limited in species, of which five or six are prevalent throughout Great Britain. The worst of these could be almost exterminated with ease, but unfortunately mistaken ideas have prevailed, and graziers commonly believe that though the sheep's nostril fly is conspicuously harmful and dangerous, the horse's bot-fly and its congeners are negligible as regards the practical health of the host. ”

“ Pondering on these matters, one day he confided to the Aunt his confirmed opinion in these words—"It seems, Aunt, to me that people who won't kill flies deserve to be fly-blown." Doubtless, it would have been better if he had expressed himself thus—People who will not kill fleas deserve to be flea-bitten; and people who will not wage war against flies deserve to be fly-tormented. ”

“ Very often the fly most numerously breeding in the manure heaps of the mews will be Borborus equinus, or some other of the same family, which are characterised by a very simple pattern of wing nervures and by the absence of squamæ or scales behind the wings; also the ankle joints of the feet are most peculiarly short and broad. B. equinus, and a great host of other dung breeding flies of a still smaller size, may be considered beneficial insects; they do not pester cattle, and their larvæ make food more scarce for injurious flies. ”

“ The yellow cow-dung fly, Scatophaga stercoraria, is inoffensive, and one of the commonest flies observable in the course of a country-side ramble. It and its congeners are distinct in habits and appearance from any of the other flies above-mentioned. In this species the male is larger than the rather more smooth and dull-coloured female. Its body is furry but slender; it has small eyes and head parts. In repose it holds its wings parallel close above the abdomen, more like the "breeze-flies," or true "gad-flies," than the ordinary muscid flies. ”

“ Strong smelling and saccharine foods immensely attract the blue-bottle and the wasp, which are thus enticed indoors and induced to become occasional visitors to our tables; but the house-fly requires little of such lures; indoors she is an inquisitive prospector, who will never pass by any moist material without testing its quality. Moreover, the use of poisoned milk, or even jam, should be rather avoided for fear of injury to dog or cat; furthermore, it is dangerous to place a piece of bread in a saucer of liquid fly-poison, as is sometimes done, to serve as a sop and as a standing stage. ”

“ In warm weather the scavenging capabilities of all the carrion and filth feeding maggots are very remarkable, and there appears no exaggeration in the statement by Linnæus, that the progeny of three flesh flies can eat up the carcase of a horse sooner than it could be devoured by a lion.
When a batch of eggs has matured in the abdomen of the female, she is most careful in the location and manner of their disposal. Guided by the sense of smell, she will not lay her eggs except in contact with food, or in places securing her progeny access to their intended food. ”

“ The compound eyes of the male fly are proportionately larger than those of the female; it is quite observable that they approach each other more closely at the top of the head, a feature of sex differentiation which is shared with bees, wasps, and many other insect creatures. ”

“ The house-fly is itself a poisoner of our food, and it, or rather she (the offender being nearly always female) , is a more dangerous and a more subtilely baneful enemy than, for instance, the human flea, which even the Brahmans or the disciples of Buddha may kill. ”

“ In domestic methods people will prefer some one plan, some another, whilst some will not personally aid in the work of fly destruction in any single way perseveringly. This latter circumstance emphasises the necessity of a dominant control by local authority for the safeguarding of all inhabitants, including the delinquents themselves in spite of themselves.
The plan, as detailed in the last chapter, of enticing breeding females to lay their eggs within depositories of discarded food remnants and garbage, can be practised on a smaller scale with great advantage everywhere. ”

“ Close observations of the habits of the house-fly reveal the very appurtenant fact that the movements of newly-hatched flies, for their first six or seven days' active life, differ from those of a more mature age, when the breeding instinct has grown strong. The latter are disposed to locate themselves for the rest of their lives in and about one attractive spot, and they are indisposed to fly high above ground or to travel far, unless it be with the object of leaving an unsatisfying locality and discovering a better place. ”

“ When the common maggots or gentles have ceased feeding, they burrow into the ground or crawl away, often to a considerable distance, apparently seeking a secluded, a more wholesomely clean, and a dryer spot. During this migrating time, they are palatable food for many birds, which would not eat them in their former food-loaded or unscoured state. Indeed, it is doubtful whether either a vulture or a raven could eat a fly-blown carcase without danger of myiasic punishment. ”

“ The fly swarms of mews, arising from accumulations of stable manure, will be difficult to alleviate without stringently enforced measures, but it is a mistaken notion to believe that town flies are bred in stables to such an extent that the invaders of our dwellings and town restaurants, shops, and markets, are merely or mainly the overflow of the mews. The concentration of many kinds of flies is very dense around ill-kept mews, and in midsummer-time a large percentage will be true house-flies. ”

“ Some breed in dung, and may be many-brooded and otherwise resemble the house-fly in prolific increase; others are more consistently vegetarian in the larval stage and slower in development; and some are possibly even single-brooded, like certain foreign large sized flies which fortunately appear only for a few weeks of summer weather, for they have a curious semi-blood-sucking habit of feeding after or alongside the skin-piercing flies, and their suctorial mouths are capable of further inflaming wounds and carrying infection from one animal to another. ”

“ The skin of the larva whilst growing is transparent, but, when about to pupate, it thickens and becomes an opaque creamy white.
The most marvellous part of the metamorphosis of the blue-bottle is concealed, when the gentle becomes the pupa; according to Réaumur the embryonic fly develops most curiously inside the puparium by a procedure not exactly like the change from the caterpillar to the chrysalid in the case of the butterfly. ”

“ The robust blue-bottle very closely resembles the house-fly in an inclination to spread the brood. Mature females, however, do sometimes show a slight temporary kind of "homing" instinct; having secured a cosy corner and a well sheltered retreat in a sunny wall, the occupant will battle for its possession, buffeting new comers.
Some of the smaller filth flies and many of the fungus flies have their lives, in the imago stage, influenced and shortened by their extra early sexual maturity; the females are fertilised whilst newly hatched and their wings limp and unfolded. ”

“ The compound eyes have doubtless some special function, but throughout the insect world the size of compound eyes is not a certain indication of keenness of sight. The vision of the fly is good for distinguishing the movement of any broad mass, but it is rather ineffective for observing a thin line, as may be proved by slowly lowering a knife blade, with a steady hand, when its body may be severed before the fly takes alarm. ”

“ Musca corvina, the raven-fly, is smaller than the house-fly; it has very distinct dark markings; the abdomen of the female is chequered, but that of the male has a black central stripe on a yellowish abdomen. It frequents gardens, parks, and meadows. It is much less prolific than the house-fly, with which it shares the sweat-fly pestering habit.
Cyrtoneura simplex is a little smaller and more common than the species last mentioned; its larvæ are bred in the dung of cows and other animals which it very severely pesters. ”

“ All insectivorous birds are fond of a diet of flies, and we may largely attribute the spring-time immigration of the beautiful swallow tribe to the fact that in the northern parts of the temperate zone swarms of soft bodied dipterous insects abound, and there replace the hard cased and more chitonous insects of hotter countries. The true swallow, the house martin, and the sand martin, all require a special food for their nestlings; and they also then require the longer summer days and the prolonged twilight of our northern clime for the frequent feeding of their young. ”

“ Imbibed bacteria are not inevitably killed in the digestive process of the fly, for its excrement has been found to abound with well recognisable infective germs. In the market, the shop, the larder, and on our tables, the house-fly seeks every opportunity of befouling and contaminating human food. ”

“ Considering the superfluity of other flies, and the multitude of other insects ever ready to do duty as devourers of carrion, garbage, and filth, the scavenging services of the larvæ of the house-fly can be well dispensed with.
In civilised communities cremation in a refuse destructor is the only sanitary method of treating town refuse. The economic value of the fly is very little, and consists merely in its food value for certain birds. ”

“ Though it starts its new life quite a wholesome newborn creature, and though it must be credited with being a most assiduous remover of dirt from its own body, yet from the human point of view its subsequent life is a persistently disgraceful career.
It is the evil course of the newly-hatched and self-cleaned fly not to restrict its diet to the honey of flowers, as do some of its relations. ”

“ Given, say, a dwelling room on a midsummer day containing ten female flies and ten idle dancing male flies; in such cases not more than half the females and one quarter of the males will get imprisoned within four or five hours by the employment of the wire-cage trap, but with a good method of setting poison nine-tenths of the females and half the males may be killed within the same period. In the case of poisoning, the dead have to be swept up, whilst fly traps have the advantage of collecting the victims ”