The insect world : being a popular account of the orders of insects, together with a description of the habits and economy of some of the most interesting species / by Louis Figuier.

  • Figuier, Louis, 1819-1894.
Date:
[1872]
    The successive stages through which an insect passes are four in number the egg ; the larva ; the pupa, nymph, or chrysalis : and the perfect insect, or imago.
    The egg State, which is common to them, as to ail other articu- late animais, it is unnecessary to explain. Nearly ail insects lay eggs, though some few are viviparous. There often exists in the extremity of the abdomen of the female a peculiar organ, called the ovipositor, which is destined to make holes for the réception of the eggs. By a wonderful instinct the mother always lays her eggs in a place where her young, on being hatched, can find an abundance of nutritious substances. It will not be needless to observe that in most cases, these aliments are quite different to those which the mother seeks for herself. In the second stage, that is to say, on leaving the egg—the larva period—the insect présents itself in a soft State, without wings, and resembles a worm. In ordinary language, it is nearly always called a worm, or grub, and in certain cases, a Caterpillar. Linnæus was the first to use the term “ larva ”—taken from the Latin word larva, “ a mask ”—as he considered that, in this form, the insect was as it were rnasked. During this period of its life the insect eats voraciously, and often changes its skin. At a certain period it ceases to eat, retires to some hidden spot, and, after changing its skin for the last time, enters the third stage of its existence, and becomes a chrysalis. In this State it resembles a mummy enveloped in bandages, or a child in its swaddling clothes. It is generally incapable of either moving or nourishing itself. It continues so for days, weeks, months, and sometimes even for years. While the insect is thus apparently dead, a slow but certain change is going on in the interior of its body. A marvellous work, though not visible outside, is being effected, for the difîerent organs ot the insect are developing by degrees under the covering which surrounds them. When their formation is complété, the insect disengages itselt from the narrow prison in which it was enclosed, and makes its appearance, provided with wings, and capable of propagating its kind ; in short, of enjoying ail the faculties which Nature lias accorded to its species. It has thrown off the mask ; the larva and pupa lias dis- appeared, and given place to the perfect insect. To show the reader the four States through which the insect passes in succession, in Fig. 16 is represented the insect known as the Hydrophilus * 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 évolution which we hâve just described, are those which take place either completely * A kind of water-beetle. —Ed.
    or incompletely in ail insects. Their métamorphosés are then at an end. There are certain insects, however, that show no différence 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 incomplète métamorphosés, the Fig. 16.—Hydrophilus in its four States. A, eggs ; B, larva ; C, pupa ; D, imago, or perfect insect. former complété métamorphosés. Some never possess wings ; indeed, there are others which undergo no metamorphosis, and are born pos- sessed of ail the organs with which it is necessary they should be provided. Some curious researches hâve been lately made on the strength of insects. i . Félix Plateau, of Brussels, has published some observations on this point, which we think of sufficient interest to reproduce here. i
    In order to measure the muscular strength of man, or of animais— as the horse, for instance—many different dynamometric apparatuses hâve been invented, composed of springs, or Systems of unequal levers. The Turks’ heads which are seen at fairs, or in the Champs Elysées, 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 Re'gnier the mechanician, and which is known by the name of Régnier’s Dynamo- meter, is much more précisé. 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 hâve not has yet given their attention to the strength of invertebrate animais. It is, relatively speaking, immense. . Many people hâve 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 édifices they are able to construct, and the dévastations they occasion. The Termes, or hite Ant,* constructs habitations many yards in height, which are so firmly and solidly built, that the buffaloes are able to mount tliem, 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 noteu. Man is proud of his works ; but what are they, after ail, in comparison with those of the ant, taking the relative heights into considération ? 1 lie largest pyramid in Egypt is only 146 yards high, that is, about mnety times the average height of man ; whereas, the nests of the 1 ermites 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. A e are, therefore, * A neuropterous insect, not a true ant.—fin.
    far beneath these little insects, as far as strength and tbe spirit of working go. The destructive power of these créatures, so insignificant in appearance, are still more surprising. During the spring of a single year they can effect the ruin of a bouse by destroying the beams and planks. The town of La Rochelle, to winch 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. Ail tliis sufficiently proves the destructive capabilities of these little animais, which we are accus- tomed 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 Re'gnier, 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, there- fore, 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 resuit, 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 insigni- ficant 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 vespil/o, fifteen times ; Trichius fasciatus, forty-one times ; and Oryctcs nasi- cor/its, four times only. The bee can draw twenty times the weight of its body ; Donacia nymphœ* forty-two times its own weight. * A beetle. —Ed.