Flies

"T HESE examples," Uncle Paul resumed, "which I could multiply indefinitely without finding a single exception, prove to you that all vermin swarming in decayed matter owes its origin to eggs laid by insects, flies, moths, butterflies, and beetles, of various kinds. Life always springs from life, never from decay."

"All the same," Marie declared, "there are lots of people that say rotting matter breeds worms."

"That is an error as old as the world, and even in our day it is widely disseminated, though much less so than in ancient times. Persons of the highest education used to regard it as beyond question that mud, dust, excrement, and other matter in decomposition would breed animal life, even rather large specimens, such as rats, frogs, eels, snakes, and many others. If the learned men of antiquity endorse in their works such gross errors, what must have been the beliefs of the uneducated!"

"Didn't those learned men know," asked Claire, "that frogs come from tadpoles hatched out of eggs laid by other frogs?"

Tadpoles

"They did not know it."

"They had only to look into a pond to find it out."

"They did not know how to look. In those old days men reasoned a great deal too much, sometimes to the point of unreason; but seldom did they take it into their heads to examine things as they really are. Patient observation, mother of all our knowledge, was unknown to them. They said, 'That is it,' without examining the matter, whereas in our day we examine before saying, 'That is it.' By this reversal of method science has, in scarcely a century, attained to a degree of power that astonishes us with its marvelous achievements. It is observation that has given us the means of protecting ourselves from the thunderbolt by using the lightning-rod; of covering enormous distances in a short time with the help of steam, which propels the railway locomotive; and of transmitting thought instantly from one end of the world to the other with the electric telegraph. Truth is acquired through observation; man does not invent it, but has to seek it laboriously, and is fortunate if he finds it.

"For want of close observation the ancients, on seeing a litter of young mice come out of some hole in the wall, attributed the procreation of these animals to the dust of the wall. If they saw a company of frogs leaping about on the muddy banks of a pond, that was enough to make them believe frogs sprang from mud fermenting in the sun."

"And I," declared Emile, "am sure they are hatched out of eggs. From one of these eggs comes first a tadpole, which little by little loses its tail, gets four legs, and finally turns into a frog. That is something like the change of form of a caterpillar into a butterfly."

"You know what was unknown to a great many wise heads in olden times."

"If I know it, it is thanks to Uncle Paul; and those who think worms come from decayed matter and frogs from mud apparently have no Uncle Paul."

"Alas, my child, how many there are that have none! By that I mean there are few who receive the thorough education that enables one to judge things from experience, observation, and sound reason. People trust the merest appearances and transmit their own premature conclusions. It is least troublesome and the quickest way. As you grow older, my dear children, you will learn how many foolish sayings gain currency in the world because people will not take the trouble to reflect and observe—observe with their own eyes.

"If one is but willing to learn, for example, that the worms in decaying matter come from eggs and not from the decay itself, all that is necessary is to have eyes and use them; for the simplest sort of experiment will decide the question, though it was centuries and centuries before any one thought of it. We merely cover with gauze or a fine wire screen any food that is beginning to spoil, such as cheese on the point of going bad, or anything else of the sort. Attracted by the odor, flies soon come circling about these tainted substances, and even lay their eggs on the gauze at the points nearest to the decaying matter which lies just out of their reach. Under these conditions, however far advanced the state of decomposition may be, no worms will make their appearance in the tainted food, because it has been kept where no eggs could be laid in it. But if the protecting gauze or wire screen is removed the flies will lay, here and there on the decaying substance, piles of little white eggs, and very soon there will be thousands of worms swarming amid the decomposing organic matter.

"By means of observations requiring rather more care it is possible to catch in the very act the little insect that lays in the cherry the egg from which comes the worm we all know so well. It has been ascertained that wormy fruit owes the inhabitants that devour it, not to decay as such, but to eggs deposited there by various insects. It has been discovered that lice do not come from flesh, nor fleas from fermenting excrement, and also that frogs are not engendered by pond mud. In short, a thousand errors of this kind have been so completely refuted that there remains not the shadow of a doubt on the manner in which the smallest grub is brought into being. Wherever you find worms, caterpillars, insects, be assured that other insects have laid their eggs there. Always and everywhere life owes its existence to life."

"You open new views to us, Uncle," said Marie, "and they will rid us of ever so many false notions."

"I have merely been trying to show you the salutary part our reasoning faculties are called upon to play. It now remains for me to give you a lesson from established facts. Certain articles of food used by us, such as cheese and meat, especially game, are always in danger of falling a prey to worms. This odious class of vermin owes its existence to flies which, according to their species, go in quest of animal flesh or of cheese wherein to lay their eggs. Two species are already well known to you, for you often see these flies buzzing noisily on the window-pane. The first kind is dark blue, the second grey with reddish eyes. Both of them have much larger bodies than the ordinary fly, and both attack meat. As to cheese-flies, I need only remind you of the worms too common to be unknown to you.

Hessian Fly

"These flies, these winged pests and audacious parasites—in them you behold the enemy that must be kept at a distance and prevented from laying eggs in our provisions if we wish to guard our larders from the invasion of vermin. Cut cheese should, accordingly, be kept under a bell-shaped wire screen or, better, under a glass dome, which at the same time insures its protection from flies and keeps it from drying up through prolonged exposure to the air. As to meat and game, which need a continual circulation and renewal of air, they should be hung in cages of fine wire netting, and every time the cage is opened care should be taken not to let in any of the blue flies that are usually lurking in the neighborhood. If the enemy were shut up with the provisions even for twenty-four hours, everything would be spoiled, such a multitude of eggs does the blue fly lay, and in so short a time. In a securely closed and carefully watched cage, game, however strong its flavor, will always be free from worms unless they were already in the game when it was placed in the wire cage."