numerous, having mostly bodies variegated with transverse stripes, their females may be seen hovering over plants infested with aphides, among which they deposit their eggs on the surface of the leaf. The larva, or maggot, produced from such eggs, feeds, as soon as hatched, on the younger kinds of aphis, and, as it increases in size, attacks and devours those which are larger. The larva of the hemerolicus feeds also on the aphides, and deposits its eggs on the leaves of such plants as are beset with them. The earwig is likewise an enemy to them, especially such as reside in the curled leaves of fruit-trees, and the purses formed by certain aphides on the poplars and other trees. To these may be added the smaller soft-billed birds that feed on insects. CHAP. XXX. CURIOSITIES RESPECTING INSECTS.-(Continued.) The Common House Fly-The Hessian Fly-The May Fly- What atom-forms of insect life appear! THE COMMON HOUSE FLY. Barbauld. GORDART has reckoned up forty-eight varieties of the fiv. without including them all in this enumeration. The multitude of these lively insects, which the first genial sunshine calls forth into life, has limits which the human eye is incapable of exploring. The female fly is easily distinguishable from the male she is larger than the latter, fuller in the body, of a lighter colour, and, when she is nearly ready to deposit her eggs, the abdomen is so transparent, that they may be perceived lying on both sides, opposite to each other. Nature has instructed her not to deposit her eggs in dry, but in damp substances, which keep them from being dried up, and at the same time afford nourishment to the maggot or worm. latter issues from the egg generally in twenty-four hours, but, in the sun, within twelve hours after it is laid. About half an hour before, annular circles become visible in the egg, an undulatory motion succeeds, the egg opens at the end, and The the worm makes its appearance. Its entrance into the world is extremely tedious; for the three or four minutes taken by the worm to work its way out of the egg, are, for it, certainly so many days. It is endowed, on the other hand, with vital powers, which enable it to defy inconveniences which cost other animals their lives. Nothing but turpentine, the general destroyer of insects, kills it in half an hour. On the fourteenth or fifteenth day, it begins to prepare for its transformation into a nymph, and in this form appears at first of a light yellow, and afterwards of a dark red. You would take it, in this state, for some kind of seed, rather than for the habitation of a living creature. The change of the nymph into a fly requires as much time as the preceding transforma tion. A thrust with the head then bursts the prison in which it is confined, and the fly, perfectly formed, sallies forth. The sun hastens its birth, which is then the business of but a moment; but in unfavourable weather, this probably painful operation often takes four or five hours. The insect is now as perfect as its parents, and not to be distinguished from them. As soon as it issues from the nymph, it flies away; and only those are unable to use their wings immediately, which have the misfortune to come out in gloomy weather. Leuwenhock reckons, that every fly has eight thousand hexagons or eyes, on each of the hemispheres composing its face, and consequently sixteen thousand on both. M. Von Gleichen, a German naturalist, observes, that the law of retaliation is in some measure established, in regard to these animals; for if they annoy us, they are in their turn persecuted by others. Small yellow insects, discovered by means of the magnifying glass, crawling among the hairs that grow on their bodies, are supposed to be destined for this purpose. The fecundity of flies is prodigious. On this head, the last-mentioned naturalist has made the following calculation: A fly lays four times during the summer, each time eighty eggs, which makes ... Half of these are supposed to be females, so that each of the four broods produces forty: 1. First eighth, or the forty females of the first brood, also lay four times in the course of the summer, which makes The first eighth of these, or 1,600 females, three times The second eighth, twice.. 320 12,800 384,000 256,000 The third and fourth eighth, at least one each...... 256,000 Carried forward 909,120 ... Brought forward One sixth of these, or 1,600 females, three times... .... The third sixth, once .... 909,120 9,600 384,000 256,000 128,000 3. The third eighth, or the forty females of the third brood, lay twice, and produce... 6,400 more... 256,000 One fourth of these, or 1,600 females, lay twice 4. The fourth eighth, or forty females of the fourth brood, once... 3,200 Half of these, or 1,600 females, at least once...... 128,000 Total produce of a single fly, in one summer.... .2,080,320 Another curious insect is, THE HESSIAN FLY.-This is a very mischievous insect, which a few years ago appeared in North America, and whose depredations threatened then to destroy the crops of wheat in that country entirely. It is, in its perfect state, a small winged insect, but the mischief it does, is while in the form of a caterpillar; and the difficulty of destroying it is increased, by its being as yet unknown where it deposits its eggs, to be hatched before the first appearance of the caterpillars. These mischievous insects begin their depredations in autumn, as soon as the wheat begins to shoot up through the ground. They devour the tender leaf and stem with great voracity, and continue to do so till stopped by the frost; but no sooner is this obstacle removed by the warmth of the spring, than the fly appears again, laying its eggs now, as has been supposed, upon the stems of the wheat just beginning to spire. The caterpillars hatched from these eggs, perforate the stems of the remaining plants at the joints, and lodge themselves in the hollow within the corn, which shews no sign of disease till the ears begin to turn heavy. The stems then break, and being no longer able to perform their office in supporting and supplying the ears with nourishment, the corn perishes about the time that it goes into a milky state. These insects attack also rye, barley, and timothy-grass, though they seem to prefer wheat. The destruction occasioned by them, is described in the American Museum, (published at Philadelphia,) for Feb. 1787, in the following words :— "It is well known that all the crops of wheat in all the land over which it has extended, have fallen before it, and that the farmers beyond it dread its approach: the prospect is, chat unless means are discovered to prevent its progress, the whole continent will be overrun;-a calamity more to be dreaded, than the ravages of war." This terrible insect appeared first in Long Island, during the American war, and was supposed to have been brought from Germany by the Hessians; whence its name. From thence it proceeded inland at the rate of about fifteen or twenty miles annually; and, in 1789, had reached two hundred miles from the place where it was first observed. At that time it continued to proceed with unabating increase; being apparently stopped neither by rivers nor mountains. In the fly state it is likewise exceedingly troublesome, by getting into houses in swarms, falling into victuals and drink, filling the windows, and flying perpetually intc the candles. THE MAY FLY.-This insect is called the May fly, from its annual appearance in that month. It lies all the It lies all the year, except a few days, at the bottom or sides of rivers, nearly resembling the nymph of the small libella; but when it is mature, it rises up to the surface of the water, and splits open its case; then, with great agility, up springs the new animal, having a slender body, with four black-veined, transparent, shining wings, with four black spots in the upper wings; the under wings are much smaller than the upper ones; and with three long hairs in its tail. The husk it leaves behind floats upon the water. After this creature is discharged from the water, it flies about to find a proper place to fix on, (as trees, bushes, &c.) to wait for its approaching change, which is effected in two or three days. The first hint I received of this wonderful operation, was by seeing their exuviæ hanging on a hedge. I then collected a great many, and put them into boxes; and by strictly observing them, I could tell when they were ready for this surprising change. I had the pleasure to shew my friends one, which I held in my fingers all the time it performed this great work; it was surprising to see how easily the back part of the fly split open, and produced the astonishing transformation. În the new fly, a remarkable difference is seen in their sexes, which is not so easy to be perceived in their first state, the male and female being much of a size; but afterwards the male is much the smallest, and the hairs of their tails much the longest. When the females are about to deposit their eggs, they seek the rivers, keeping constantly playing up and down upon the water. It is very plainly seen, that every time they dart down, they eject a cluster of eggs, which appears like a little bluish speck, or a small drop of milk, as they sink to the bottom of the river. Thus they continue until they have spent their strength, being so weak, that they can rise no more, but fall a prey to the fish. But by much the greatest number perish on the waters, which are covered with them. This is the end of the females. The males never resort to the river, but, after a time, drop down, languish, and die, under the trees and bushes. The species of libella abounds most with females, which is very necessary, considering the many enemies they have in their short appearance; for both birds and fishes are fond of them, and, no doubt, under water they are the prey of aquatic animals. What is further surprising in this remarkable creature is, that during a life which consists only of three or four days, it eats nothing, and seems to have no apparatus for this purpose, but brings up with it, out of the water, sufficient support to enable it to shed its skin, and perform the principal ends of life with great vivacity. THE VEGETABLE FLY.-This is a very curious natural production, chiefly found in the West Indies. It resembles the drone, both in size and colour, more than any other British insect, excepting that it has no wings. "In the month of May, it buries itself in the earth, and begins to vegetate. By the end of July, the tree has arrived at its full growth, and resembles a coral branch; it is about three inches in height, and bears several little pods, which, dropping off, become worms, and thence flies, like the British caterpillar." Such was the account originally given of this extraordinary production. But several boxes of these flies having been sent to Dr. Hill for examination, his report was as follows:-"There is in Martinique a fungus of the clavaria kind, different in species from those hitherto known. It produces soboles from its sides; I call it therefore clavaria sobolifera. It grows on putrid animal bodies, as our fungus (ex pede equino) from the dead horse's hoof. The cicada is common in Martinique, and in its nymph state, in which the old authors call it tettigometra, it buries itself under the dead leaves, to await its change; and, when the season is unfavourable, many perish. The seeds of the clavaria find a proper bed in these dead insects, and grow. The tettigometra is among the cicada in the British Museum; the clavaria is but just now known. This is the fact, and all the fact; though the untaught inhabitants suppose a fly to vegetate, and though there is a Spanish drawing of the plants growing into a trifoliate tree; and it has been figurea. with the creature flying with this tree upon its back.”—Thus does ignorance delight in the marvellous! |