London Labour and the London Poor, volume 3
THESE winged tormentors are not, like most of our apterous enemies, calculated to excite disgust and nausea when we see or speak of them; nor do they usually steal upon us during the silent hours of repose (though the gnat or mosquito must be here excepted), but are many of them very beautiful, and boldly make their attack upon us in open day, when we are best able to defend ourselves.
The active fly, so frequently an unbidden guest at your table (Mouffet, ), whose delicate palate selects your choicest viands, at time extending his proboscis to the margin of a drop of wine, and then gaily flying to take a more solid repast from a pear or a peach— now gambolling with his comrades in the air, now gracefully carrying his furled wings with his taper feet—was but the other day a disgusting grub, without wings, without legs, without eyes, wallowing, well pleased, in the midst of a mass of excrement.
"The common house-fly," says Kirby, "is with us sufficiently annoying at the close of summer, so as to have led the celebrated Italian Ugo Foscolo, when residing here, to call it of the " miseries of life."" But we know nothing of it as a tormentor, compared with the inhabitants of southern Europe, "I met," says Arthur Young, in his interesting , between Pradelles and Thurytz, "mulberries and flies at the same time. By the term , I mean those myriads of them which form the most disagreeable circumstances of the southern climates. They are the torments in Spain, Italy, and the olive district of France; it is not that they bite, sting, or hurt, but they buzz, teaze, and worry; your mouth, eyes, ears, and nose are full of them: they swarm on every eatable—fruit, sugar, everything is attacked by them in such myriads, that if they are not incessantly driven away by a person who has nothing else to do, to eat a meal is impossible. They are, however, caught on prepared paper, and other contrivances, with so much ease and in such quantities, that were it not for negligence they
|could not abound in such incredible quantities. If I farmed in these countries, I should manure or acres every year with dead flies. I have been much surprised that the learned Mr. Harmer should think it odd to find, by writers who treated of southern climates, that driving away flies was of importance. Had he been with me in Spain and in Languedoc in July and August, he would have been very far from thinking there was anything odd in it."— (, i. .)|
It is a remarkable, and, as yet, unexplained fact, that if nets of thread or string, with meshes a full inch square, be stretched over the open windows of a room in summer or autumn, when flies are the greatest nuisance, not a single will venture to enter from without; so that by this simple plan, a house may be kept free from these pests, while the adjoining ones which have not had nets applied to their windows will swarm with them. In order, however, that the protection should be efficient, it is necessary that the rooms to which it is applied should have the light enter by only; for in those which have a thorough light, the flies, strange to say, pass through the meshes without scruple.
For a fuller account of these singular facts, the reader is referred to a paper by W. Spence, in vol. i. p. , and also to in the same work by the Rev. E. Stanley, late Lord Bishop of Norwich, who, having made some of the experiments suggested by Mr. Spence, found that by extending over the outside of his windows nets of a very fine packthread, with meshes inch and a quarter to the square, so fine and comparatively invisible that there was no apparent diminution either of light or the distant view, he was enabled for the remainder of the summer and autumn to enjoy the fresh air with open windows, without the annoyance he had previously experienced from the intrusion of flies—often so troublesome that he was obliged on the hottest days to forego the luxury of admitting the air by even partially raising the sashes.
"The number of house-flies," he adds, "might be greatly lessened in large towns, if the stabledung in which their larvæ are chiefly supposed to feed were kept in pits closed by trap-doors, so that the females could not deposit their eggs in it. At Venice, where no horses are kept, it is said there are no house-flies; a statement which I regret not having heard before being there, that I might have inquired as to its truth."—( i. , .)
This short account of flies would be incomplete without a description of their mode of proceeding when they regale themselves upon a piece of loaf-sugar, and an account of the apparatus with which the Creator has furnished them in order to enable them to walk on bodies possessing smooth surfaces, and in any position.
"In the case of their drinking fluids, like water, saliva is not wanted; and it may be remarked, when we drink cold water it actually astringes and shuts up the openings of the salivary pipes. Hence it is that drinking does not quench thirst when the saliva is rendered viscid and scanty by heat, by fatigue, or by the use of stimulant food and liquor; and sometimes a draught of cold water, by carrying off all the saliva from the mouth, and at the same time astringing the orifices of the ducts, may actually produce thirst. Ices produce this effect on many persons. It is, no doubt, in consequence of their laborious exertions, as well as of the hot nature of their acid fluids producing similar effects, that ants are so fond of water. We have seen quaff a drop of dew almost as large as its whole body; and when we present those in our glass formicaries with water, they seem quite insatiable in drinking it."
Rennie, in his , after describing the pedestrian contrivances with which various insects are furnished, says,
—"The most perfect contrivance of this kind, however, occurs in the domestic fly (), and its congeners, as well as in several other insects. Few can have failed to remark that flies walk with the utmost ease along the ceiling of a room, and no less so upon a perpendicular looking-glass; and though this were turned downwards, the flies would not fall off, but could maintain their position undisturbed wtth their backs hanging downwards. The conjectures devised by naturalists to account for this singular circumstance, previous to the ascertaining of the actual facts, are not a little amusing. "Some suppose," says the Abbé de la Pluche, "that when the fly marches over any polished body, on which neither its claws nor its points can fasten, it sometimes compresses her sponge and causes it to evacuate a fluid, which fixes it in such a manner as prevents its falling without diminishing the facility of its progress; but it is much more probable that the sponges correspond with the fleshy balls which accompany the claws of dogs and cats, and that they enable the fly to proceed with a softer pace, and contribute to the preservation of the claws, whose pointed extremities would soon be impaired without this prevention." ( vol. i. p. .) "Its ability to walk on glass," says S. Shaw, "proceeds partly from some little ruggedness thereon, but chiefly from a tarnish, or dirty, smoky substance, adhering to the surface; so that, though the sharp points on the sponges cannot penetrate the surface of the glass, it may easily catch hold of the tarnish." ( vol. iii. p. , Lond. .) But," adds Rennie, "it is singular that none of these fanciers ever took the trouble to ascertain the existence of either a gluten squeezed out by the fly, or of the smoky tarnish on glass. Even the shrewd Réaumur could not give a satisfactory explanation of the circumstance."
"The earliest correct notion on this curious subject was entertained by Derham, who, in mentioning the provision made for insects that hang on smooth surfaces, says, "I might here name divers flies and other insects who, besides their sharp-hooked nails, have also skinny palms to their feet, to enable them to stick to glass and other smooth bodies by means of the pressure of the atmosphere—after the manner as I have seen boys carry heavy stones with only a wet piece of leather clapped on the top of the stone." (, vol. ii. p. , note , edit.) The justlycelebrated Mr. White, of Selborne, apparently without the aid of microscopical investigation, adopted Derham"s opinion, adding the interesting illustration, that in the decline of the year, when the flies crowd to windows and become sluggish and torpid, they are scarcely able to lift their legs, which seem glued to the glass, where many actually stick till they die; whereas they are, during warm weather, so brisk and alert, that they easily overcome the pressure of the atmosphere."—(, vol. ii. p. .)
"This singular mechanism, however," continues Rennie, "is not peculiar to flies, for some animals a times as large can walk upon glass by the same means." St. Pierre mentions "a very small lizard, about a finger"s length, which climbs along the walls, and even along glass, in pursuit of flies and other insects" (, p. ); and Sir Joseph Banks noticed another lizard, named the Gecke (, LINN.), which could walk against gravity, and which made him desirous of having the subject thoroughly investigated. On mentioning it to Sir Everard Home, he and Mr. Bauer commenced a series of researches, by which they proved incontrovertibly, that in climbing upon glass, and walking along the ceilings with the back downwards, a vacuum is produced by a particular apparatus in the feet, sufficient to cause atmospheric pressure upon their exterior surface.
The apparatus in the feet of the fly consists of or mombranous suckers, connected with the last joint of the foot by a narrow neck, of a funnel-shape, immediately
|under the base of each jaw, and movable in all directions. These suckers are convex above and hollow below, the edges being margined with minute serratures, and the hollow portion covered with down. In order to produce the vacuum and the pressure, these membranes are separated and expanded, and when the fly is about to lift its foot, it brings them together, and folds them up, as it were, between the claws. By means of a common microscope, these interesting movements may be observed when a fly is confined in a wine-glass." (, p. .)|
It must have attracted the attention of the most incurious to see, during the summer, swarms of flies crowding about the droppings of cattle, so as almost to conceal the nuisance, and presenting instead a display of their shining corslets and twinkling wings. The object of all this busy bustle is to deposit their eggs where their progeny may find abundant food; and the final cause is obviously both to remove the nuisance, and to provide abundant food for birds and other animals which prey upon flies or their larvæ.
The same remarks apply with no less force to the "blow-flies," which deposit their eggs, and in some cases their young, upon carcases. The common house-fly (the female of which generally lays eggs) belongs to the division, the natural food of its larvæ being horse-dung; consequently, it is always most abundant in houses in the vicinity of stables, cucumberbeds, &c., to which, when its numbers become annoying, attention should be primarily directed, rather than having recourse to flywaters."—(RENNIE"S , p. .)
Besides the house-fly, and the other genera of the dipterous order of insects, there is another not unfrequent intruding visitor of the fly kind which we must not omit to mention, commonly known as the , LINN.). The disgust with which these insects are generally viewed will perhaps be diminished when our readers are informed that they are destined to perform a very important part in the economy of nature. Amongst a number of the insect tribe whose office it is to remove nuisances the most disgusting to the eye, and the most offensive to the smell, the varieties of the blue-bottle fly belong to the most useful.
"When the dead carcases of animals begin to grow putrid, every knows what dreadful miasmata exhale from them, and taint the air we breathe. But no sooner does life depart from the body of any creature—at least from any which, from its size, is likely to become a nuisance—than myriads of different sorts of insects attack it, and in various ways. come the , and pierce the skin. Next follow the , covering it with millions of eggs, whence in a day or proceed innumerable devourers. An idea of the despatch made by these gourmands may be gained from the combined consideration of their numbers, voracity, and rapid development. The larvæ of many flesh-flies, as Redi ascertained, will in hours devour so much food, and gnaw so quickly, as to increase their weight -fold! In days after being hatched they arrive at their full growth and size, which is a remarkable instance of the care of Providence in fitting them for the part they are destined to act; for if a longer time was required for their growth, their food would not be a fit aliment for them, or they would be too long in removing the nuisance it is given them to dissipate. Thus we see there was some ground for Linnæus"s assertion, under , that of these flies will devour a dead horse as quickly as would a lion."—(KIRBY and SPENCE, i.)
The following extraordinary fact, given by Kirby and Spence, concerning the voracity of the larvæ of the blow-fly, or blue-bottle (), is worth while appending:—
species of fly infests our houses
|(), which so nearly resembles the common house-fly (), that the difference is not easily detected except by an entomologist; indeed the resemblance is so close as to have led to the vulgar error that the common house-fly occasionally indulges itself by a feast upon our blood, after it has fed to satiety upon the delicacies which it picks from our tables. It is even a greater torment than the horse-fly.|
"This little pest," says Kirby, referring to the , "I speak feelingly, incessantly interrupts our studies and comfort in showery weather, making us even stamp like the cattle by its attacks on our legs, and if we drive it away ever so often, returning again and again to the charge." In Canada they are infinitely worse. "I have sat down to write," says Lambert, (who, though he calls it the house-fly, is evidently speaking of the Stomoxys), "and have been obliged to throw away my pen in consequence of their irritating bite, which has obliged me every moment to raise my hand to my eyes, nose, mouth, and ears, in constant succession. When I could no longer write, I began to read, and was always obliged to keep hand constantly on the move towards my head. Sometimes, in the course of a few minutes, I would take half-a-dozen of my tormentors from my lips, between which I caught them just as they perched."—( &c. i. .)
But of all the insect-tormentors of man, none are so loudly and universally complained of as the species of the genus , L., whether known by the name of gnats or mosquitos. It has been generally supposed by naturalists that the mosquitos of America belong to the Linnæan genus but Humboldt asserts that the term , signifying , is applied there to a , LATR. (, MEIG.), and that the , which are equally numerous and annoying, are called , which means The former, he says, are what the French call , and the latter , E.T., v. .)
Humboldt"s remark, however, refers only to South America. Mr. Westwood informs us that is certainly applied to a species of in the United States, the inhabitants giving the name of -fly to a small Pliny, after Aristotle, distinguishes well between and , when he says the former have their sting in the , and the latter in the and that to the this instrument is given as the instrument of vengeance, and to the other of avidity.
But the instrument of avidity in the genus of which I am speaking is even more terrible than that of vengeance in most insects that are armed with it. It instils into its wound a poison (as appears from the consequent inflammation and tumour), the principal use of which is to render the blood more fluid and fitter for suction. This weapon, which is more complex than the sting of hymenopterous insects, consisting of pieces besides the exterior sheath—some of which seem simply lancets, while others are barbed like the spiculæ of a bee"s sting—is at once calculated for piercing the flesh and forming a syphon adapted to imbibe the blood. There are several species of this genus whose bite is severe; but none is to be compared to the common gnat (, L.), if, as has been generally affirmed, it be synonymous with the mosquite, though, in all probability, several species are confounded under both names.
In this country they are justly regarded as no trifling evil; for they follow us to all our haunts, intrude into our most secret retirements, assail us in the city and in the country, in our houses and in our fields, in the sun and in the shade; nay, they pursue us to our pillows, and keep us awake by the ceaseless hum of their rapid wings (which, according to the Baron C. de Latour, are vibrated times per minute), and their incessant endeavours to fix themselves upon our face, or some uncovered part of our body; whilst, if in spite of them we fall asleep, they awaken us by the acute pain which attends the insertion of their oral stings, attacking with most avidity the softer sex, and trying their temper by disfiguring their beauty.
In Marshland in Norfolk, the inhabitants are said to be so annoyed by the gnats, that the better sort of them, as in many hot climates, have recourse to a gauze covering for their beds, to keep them off during the night.
 "Insect Miscellanies," p. 38.
 Ibid, p. 368.