“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 144 eggs) belongs to the first division, the natural food of its larvæ being horse-dung; consequently, it is always most abundant in houses in the vicinity of stables, cucumber-beds, &c., to which, when its numbers become annoying, attention should be primarily directed, rather than having recourse to fly-waters.”—(Rennie’s Insect Miscellany, p. 265.)
Besides the common 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 blue-bottle (Musca vomitoria, 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 one 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. First come the histers, and pierce the skin. Next follow the flesh-flies, covering it with millions of eggs, whence in a day or two 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 twenty-four hours devour so much food, and gnaw so quickly, as to increase their weight two hundred-fold! In five 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 Musca vomitoria, that three 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 (Musca vomitoria), is worth while appending:—
“On Thursday, June 25th, died at Asbornby, Lincolnshire, John Page, a pauper belonging to Silk-Willoughby, under circumstances truly singular. He being of a restless disposition, and not choosing to stay in the parish workhouse, was in the habit of strolling about the neighbouring villages, subsisting on the pittance obtained from door to door. The support he usually received from the benevolent was bread and meat; and after satisfying the cravings of nature, it was his custom to deposit the surplus provision, particularly the meat, between his shirt and skin. Having a considerable portion of this provision in store, so deposited, he was taken rather unwell, and laid himself down in a field in the parish of Stredington; when, from the heat of the season at that time, the meat speedily became putrid, and was of course struck by the flies. These not only proceeded to devour the inanimate pieces of flesh, but also literally to prey upon the living substance; and when the wretched man was accidentally found by some of the inhabitants, he was so eaten by the maggots, that his death seemed inevitable. After clearing away, as well as they were able, these shocking vermin, those who found Page conveyed him to Asbornby, and a surgeon was immediately procured, who declared that his body was in such a state that dressing it must be little short of instantaneous death; and, in fact, the man did survive the operation but for a few hours. When first found, and again when examined by the surgeon, he presented a sight loathsome in the extreme. White maggots of enormous size were crawling in and upon his body, which they had most shockingly mangled, and the removal of the external ones served only to render the sight more horrid.” Kirby adds, “In passing through this parish last spring, I inquired of the mail-coachman whether he had heard this story; and he said the fact was well known.”
One species of fly infests our houses (Stomoxys calcitrans), which so nearly resembles the common house-fly (Musca domestica), 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 Stomoxys, “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 one 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.”—(Travels. &c. i. 126.)
But of all the insect-tormentors of man, none are so loudly and universally complained of as the species of the genus Culex, 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 Culex; but Humboldt asserts that the term mosquito, signifying a little fly, is applied there to a Senicilium, Latr. (Senicilia, Meig.), and that the Culices, which are equally numerous and annoying, are called Zancudoes, which means long-legs. The former, he says, are what the French call Moustiques, and the latter Maringouins. (Personal Narrative, E. T., v. 93.)
Humboldt’s remark, however, refers only to South America. Mr. Westwood informs us that Mosquito is certainly applied to a species of Culex in the United States, the inhabitants giving the name of black-fly to a small Senicilium. Pliny, after Aristotle, distinguishes well between Hymenoptera and Diptera, when he says the former have their sting in the tail, and the latter in the mouth; and that to the one 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 five 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 (Culex pipiens, L.), if, as has been generally affirmed, it be synonymous with the mosquito, though, in all probability, several species are confounded under both names.