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for the microscope. Having placed one in a pill-box with the heads of three dead flies, he found sometime after, that they had completely cleared the interior of some of the eyes from all the blood-vessels, leaving the lenses in the cornea most beautifully transparent.
KNOWLEDGE FOR THE PEOPLE.
Why are "monstrous ants in India, as large as foxes," described by old Greek writers?
Because the termites there rear such stupendous fabrics, as certainly might be supposed to be the work of a much larger animal than their real architect. Were our houses built according to the same proportions, they would be twelve or fifteen times higher than the London monument, and four or five times higher than the pyramids of Egypt, with corresponding dimensions in the basements of the edifices.
Why are flies continually brushing themselves with their feet and legs?
Because by this means they rub off the dust, and clean their eyes, head, corslet, and wings,-and to enable them to do this, their foot closely resembles a currycomb. Thus, in the common blow-fly, there are two rounded combs, the inner surface of which is covered with down, to serve the double purpose of a fine brush, and to assist in forming a vacuum, when the creature walks on a glass, or on the ceiling of a room. In other flies, there are three such combs on each foot. The insects are pretty thickly covered with hair, and the serratures (or teeth) of the combs free them from entanglement and dust. Even the hairs on the legs themselves are similarly used; for, flies not only brush Iwith the extremities of their feet, where the curious currycombs are situated, but use part of their legs in the same way, particularly for brushing one another.Mr. Rennie, in Journal of the Royal Institution.
Why is the dogs'-bane so fatal to flies?
Because of the elasticity of the filaments of the plant, which close and catch the fly the instant the trunk is protruded to feed on the expanded blossom: the poor prisoner struggles till exhausted to death, the filaments then relax, and the body falls to the ground. The plant will at times be dusky from the number of imprisoned wretches.
Why has the flea been quoted as an instance of insects excelling in muscular power, in proportion to their diminutiveness?
Because it has been known to draw 70 or 80 times its own weight, resist the ordinary pressure of the fingers in our endeavours to crush it, and leap two hundred times its own length. Hence it is called by the Arabians, "the father of leapers." Supposing the same relative force to be infused into the body of a man six feet high, he would be enabled to leap three times the height of St. Paul's.
The feats of fleas drawing golden chains and coaches have been authenticated. Latreille tells us of a flea which dragged a silver cannon twenty-four times its own weight, mounted on wheels, and was not alarmed when this was charged with gunpowder, and fired off.
Why do some spiders rest in the centre of their webs? Because the outstretched cordage may warn them of the temporary entanglement of their prey, on which they instantly rush, and devour, after the infliction of a mortal wound. Many lie in wait beneath leaves, and others spin comfortable tunnels, or watch-towers, as they may be called, in which they repose till the vibration of their nets below calls them into active service.
Why do other spiders spin no webs at all?
Because they trust to strength, activity, and cunning, for their daily, or, it may be, monthly fare; for spiders, though voracious in times of abundance, are capable of frequent and long-continued abstinence.
Vaillant had a spider that lived nearly a year without food, and was so far from being weakened by abstinence, that it immediately killed another large spider, equally vigorous, but not so hungry, that was put in along with it. Baker is known to have kept a beetle in a state of total abstinence for three years: it afterwards made its escape.
Several of this webless species leap, and others hunt down their insect food by speed of foot, and a few on the surface of water. A large species, common in Norfolk, constructs a raft of weeds, or floating island, on which it is wafted about, and from it seizes upon drowning insects.
Why is the bite of some spiders poisonous ?
Because the claw of the mandible distils a deleterious liquid, analogous in its nature to that which exudes from the mouth of the scolopendra, and the tail or sting of the scorpion.
The bite of the tarantula spider, was said to produce symptoms equally severe with those of the most malignant fever, and of such a nature, as to be cured only by means of music. Some authors have even given a list of the most restorative tunes.
Why are some spiders called suckers?
Because, with their mandibles, resembling a pair of pincers, they compress the small animal on which they prey, and so force the alimentary juices to pass by degrees into the oesophagus. The body of their prey having undergone this operation, is then thrown aside.
A species in the West Indies kills humming-birds, and sucks their eggs. It is the size of a small child's fist; the soles of the feet glitter with gold, &c.
Some species of spider can reproduce lost or muti
lated parts, like the crab and lobster. This fact was first observed in this country by Sir Joseph Banks, which gave rise to Dr. Wolcot's well-known satire.
Why do spiders spin threads in the air?
Because they may ascend and descend, cross from tree to tree, across streams, &c.; but whether this is accomplished by projectile force, by the electricity of the atmosphere, or by the mechanical action of the external currents of air, is still a subject of dispute. Messrs. Rennie, and Blackwall, maintain the necessity of a current of air as a moving force; Mr. Murray, Mr. Bowman, and others, maintain a contrary opinion; and Mr. Viray thinks it more probable, that spiders actually fly, by vibrating their feet through the air; he does not assert that they have wings.
Why do garden-spiders in part renew their nets in every twenty-four hours?
Because they catch their prey by the gummed threads of the web, which lose their viscid properties by the action of the air.*
Why ought not spiders'-webs to be destroyed in stables? Because they benefit the horses: the more spiderswebs, the fewer flies.
Why does the scorpion carry its young on the back? Because they are there protected and defended by the tail, at the extremity of which is the sting. Scorpions have frequent battles with ants, which may sometimes be seen dragging from the field one of their vanquished foes.-Dr. Scot.
* Leuwenhoeck states, that the threads of the minutest spiders, some of which are not equal in bulk to a grain of sand, are so fine, that four millions of them would not exceed the thickness of a human hair. Each of the four spinners from which the web is spun, is pierced by about 1,000 holes, consequently, every compound or ordinary thread is composed of 40,000 still finer. Thus, a spider's thread, of the thickness of a human hair, may, in some instances, be composed of not fewer than 16,000 millions.
Why are scorpions killed by covering them with oil? Because their respiration is thus prevented.
CRAB, LOBSTER, &c.
Why do not the crab, and lobster appear "thin," when ill fed?
Because the stomach is formed on a bony apparatus, in short, a species of skeleton; and does not therefore collapse when empty. Hence the policy of choosing crabs and lobsters by their weight.
Why is the food of the crab and lobster sure to be perfectly masticated?
Because to certain parts of the bony structure of the stomach, round its aperture communicating with the small intestines, (or the pylorus) the teeth are affixed. They are extremely hard, and serrated, or jagged, and as they surround the tube near the pylorus, nothing can pass that has not been duly prepared. These bones and teeth (the latter three in number) are moved by peculiar muscles, and in the craw-fish are known to be annually reproduced.
Why do some crabs attach, by a glutinous matter, the leaves of sea-weeds to their body?
Because they may thus completely conceal their form, and secure themselves from the detection of their enemies.
Why are the two calcareous concretions (commonly called crabs' eyes), found in summer at both sides of the stomach of the craw-fish?
Because they furnish the principal materials from which the new shell is hardened. Some are naturally red, whilst others remain black, even when boiled; and some reach the age of twenty years.