pginternal" title="" tag="{http://www.w3.org/1999/xhtml}a">[5] firstly, in the egg state; secondly, as the larva, or caterpillar; thirdly in the pupa; and fourthly as the perfect insect or imago. The different degrees of transformation and evolution which we have just described, are those which take place either completely or incompletely in all insects. Their metamorphoses are then at an end. There are certain insects, however, that show no difference in their various stages, except by absence of wings in the larva; and in these the chrysalis is only characterised by the growth of the wings, which, at first folded back and hidden under the skin, afterwards become free, but are not wholly developed till the last skin is cast. These insects are said to undergo incomplete metamorphoses, the former complete metamorphoses. Some never possess wings; indeed, there are others which undergo no metamorphosis, and are born possessed of all the organs with which it is necessary they should be provided.

Fig. 16.—Hydrophilus in its four states.
A, eggs; B, larva; C, pupa; D, imago, or perfect insect.

Some curious researches have been lately made on the strength of insects. M. Felix Plateau, of Brussels, has published some observations on this point, which we think of sufficient interest to reproduce here.

In order to measure the muscular strength of man, or of animals—as the horse, for instance—many different dynamometric apparatuses have been invented, composed of springs, or systems of unequal levers. The Turks' heads which are seen at fairs, or in the Champs Élysées, at Paris, and on which the person who wishes to try his strength gives a strong blow with his fist, represent a dynamometer of this kind. The one which Buffon had constructed by Régnier the mechanician, and which is known by the name of Régnier's Dynamometer, is much more precise. It consists of an oval spring, of which the two ends approach each other; when they are pulled in opposite directions, a needle, which works on a dial marked with figures, indicates the force exercised on the spring. It has been proved, with this instrument, that the muscular effort of a man pulling with both hands is about 124 lbs., and that of a woman only 74 lbs. The ordinary effort of strength of a man in lifting a weight is 292 lbs.; and a horse, in pulling, shows a strength of 675 lbs.; a man, under the same circumstances, exhibiting a strength of 90 lbs.

Physiologists have not as yet given their attention to the strength of invertebrate animals. It is, relatively speaking, immense. Many people have observed how out of proportion a jump of a flea is to its size. A flea is not more than an eighth of an inch in length, and it jumps a yard; in proportion, a lion ought to jump two-thirds of a mile. Pliny shows, in his "Natural History," that the weights carried by ants appear exceedingly great when they are compared with the size of these indefatigable labourers. The strength of these insects is still more striking, when one considers the edifices they are able to construct, and the devastations they occasion. The Termes, or White Ant,[6] constructs habitations many yards in height, which are so firmly and solidly built, that the buffaloes are able to mount them, and use them as observatories; they are made of particles of wood joined together by a gummy substance, and are able to resist even the force of a hurricane.

There is another circumstance which is worth being noted. Man is proud of his works; but what are they, after all, in comparison with those of the ant, taking the relative heights into consideration? The largest pyramid in Egypt is only 146 yards high, that is, about ninety times the average height of man; whereas, the nests of the Termites are a thousand times the height of the insects which construct them. Their habitations are thus twelve times higher than the largest specimen of architecture raised by human hands. We are, therefore, far beneath these little insects, as far as strength and the spirit of working go.

The destructive power of these creatures, so insignificant in appearance, are still more surprising. During the spring of a single year they can effect the ruin of a house by destroying the beams and planks. The town of La Rochelle, to which the Termites were imported by an American ship, is menaced with being eventually suspended on catacombs, like the town of Valencia in New Grenada. It is well known what destruction is caused when a swarm of locusts alight in a cultivated field; and it is certain that even their larvæ do as severe injury as the perfect insect. All this sufficiently proves the destructive capabilities of these little animals, which we are accustomed to despise.

M. Plateau has studied the power of traction in some insects, the power of pushing in the digging insects, and the lifting power of others during flight. He has thus been able to make some most interesting comparisons, of some of which we will relate the results.

The average weight of man being 142 lbs., and his power of traction, according to Régnier, being 124 lbs., the proportion of the weight he can draw to the weight of his body is only as 87 to 100. With the horse the proportion is not more than 67 to 100, a horse 1,350 lbs. in weight only drawing about 900 lbs. The horse, therefore, can draw little more than half his own weight, and a man cannot draw the weight of his own body.

This is a very poor result, if compared with the strength of the cockchafer. This insect, in fact, possesses a power of traction equal to more than fourteen times its own weight. If you amuse yourself with the children's game of making a cockchafer draw small cargoes of stones, you will be surprised at the great weight which this insignificant looking animal is able to manage.

To test the power of traction in insects, M. Plateau attached them to a weight by means of a thread fastened to one of their feet. The Coleoptera (Beetles) are the best adapted for these experiments.

The following are some of the results obtained by the Belgian physician:—Carabus auratus can draw seven times the weight of its body; Nebria brevicollis, twenty-five times; Necrophorus vespillo, fifteen times; Trichius fasciatus, forty-one times; and Oryctes nasicornis, four times only. The bee can draw twenty times the weight of its body; Donacia nymphæ [7] forty-two times its own weight.

From this it follows that if the horse possessed the same strength as this last insect, or if the insect were the size of a horse, they would either of them be able to draw 155,250 lbs. M. Plateau has ascertained the pushing power in insects, by introducing them into a pasteboard tube, the interior of which was made rough, and in which was fixed a glass plate, which allowed the light to penetrate into the prison. The animal, if excited, struggled with all its strength against the transparent plate, which, on being pushed forward, turned a lever adapted to a miniature dynamometer, which indicated the amount of effort exercised.

The results thus obtained prove that the pushing power, like the power of traction, is greater in inverse proportion to the size and weight of the animal. A few