Part 31

Huber adds that, having returned to the pillaged nest to examine it more closely, he saw some ashy-black workers bringing back to their home the few larvæ which they had succeeded in saving. Having later discovered the nest of these Amazons, which is the name he gives to the warrior ants, he found there many of the ashy-black ants living on very good terms with their kidnappers.

The Amazons begin their expeditions at the end of June, during the hottest hours of the day. They come out in long files, eight or ten abreast, preceded by their scouts. These columns start at a run, in a straight line, and without feeling their way. They have no chieftain. The van is re-formed every moment. Those who are in front do not remain there; at the end of a certain time they go and range themselves in the rear, and are replaced by those which were behind. The whole troop is thus in constant communication through its entire length. Rarely does the expedition divide into two bodies. Arrived under the walls of the fortress, the column halts and masses itself into one corps. The assault is made with incredible impetuosity. In the twinkling of an eye the place is escaladed, taken by storm, and pillaged, and the ashy-black ants are either put to flight or led away into captivity. The same ant-hill may be invaded as many as three times running on the same day; but then the ashy-black ants, on their guard, have barricaded themselves in, and in that case the aggressors return home without pillaging them.

The Mining Ants (Fig. 370) are less timid than the ashy-black; and, as they defend themselves with more energy, there are frequently deadly combats, and the field of battle is left covered with heads, legs, and limbs, scattered about here and there with the dead and wounded. The miners pursue the pillagers, and snatch their plunder from them. But they are sometimes driven back vigorously, and the russet ants gain their lair with the plunder.

The tactics of the Red Ants (_Formica sanguinea_) differ from those of the russet. They only sally forth in small detachments, which begin by engaging in skirmishes with the scouts thrown out round the enemy's ant-hill. Couriers, despatched from time to time to the camp of the red ants, bring up reinforcements. When the troop feels itself sufficiently strong, it invades the nest of the ashy-black ants, and carries off their offspring, which the latter have not had time to secure. Sometimes, also, the red ants instal themselves in the nest whose inhabitants they have ejected, and transfer their own population to it. The motive for this emigration is that the old nest has become useless, or that it is exposed to some danger. The red ants are not the only ants which thus desert their birth-place. Many species abandon it likewise, for analogous motives, and construct elsewhere another dwelling, to which they transport all the population of the first nest.

When we reflect on the habits of ants, we are forced to admit that intelligence and reason appear still more in their acts than in those of bees. The life of ants, as well as that of bees, as far as we are concerned, is an unintelligible enigma. The acts of animals, in general, are sometimes an abyss unfathomable to our reason. The Orientals say, "The last word may be written on man: on the elephant, never!" Let us add that they should no more say that the elephant will be an inexhaustible theme, but that the history of the ant will continue so always.

The best-known genera of the Fossores, or Fossorial Hymenoptera, are _Philanthus_ (Fig. 371), which feeds its larvæ on bees, having first numbed them by its sting; _Pompilus_ and _Sphex_, which attack spiders; and _Mutilla_ (Fig. 372), whose females resemble ants, being variegated with red and yellow, the males, being provided with wings and smaller in size, and black. The _Mutillæ_ are parasitical on solitary bees, their larvæ devouring their larvæ.

Other Hymenoptera lay their eggs under the skin of certain insects, especially when these are in the larva or caterpillar state, thus rendering service to agriculture by destroying a great number of noxious insects. In lieu of a sting they have an auger, intended to pierce the skin of their victims. It is thus that the _Ichneumons_ introduce their eggs under the skin of caterpillars. The _Pimplas_ (Fig. 373), which belongs to this group, have a very long ovipositor, which, with its two appendages, constitute three lancets, and enable them to get at the larvæ in their retreats. The _Ophions_ (Fig. 374) have a sickle-shaped abdomen. They lay their eggs on the skin of caterpillars, which they attack with the short cutting auger with which they are provided.

The _Cynips_, or Gall-insects, are small black or tawny Hymenoptera, the females of which have an auger, rolled up spirally and hidden in a fissure of the abdomen, with which they prick the young shoots of plants. A peculiar liquid which they pour into the hole round the egg they have laid, causes an excrescence to grow, which is called a "gall." The larva is developed in the centre of this gall, and transformed into a pupa; and afterwards into a perfect insect, which makes its exit by a hole in the wall of its prison. Fig. 375 represents the Cynips of the oak tree (_Cynips quercusfolii_), and Figs. 376 and 377 the galls it produces. The galls of the rose are hairy, and are sometimes called "Robin's Cushion." The gall-nut, rich in tannin, which is used in the manufacture of ink, is the produce of a foreign Cynips, which lives on an oak found in the East. Apples of Sodom, which travellers bring back from the shores of the Dead Sea, are large galls[106] full of dry dust and larvæ.

[106] Made by _Cynips insana_.--ED.

The _Urocerata_ and the _Tenthredinetæ_ form two tribes of insects, of which the first are of great size, have a cylindrical body, the abdomen being attached to the thorax in its whole breadth, without any pedicle.

The insects of the genus _Sirex_ (Fig. 378), belonging to the former of these, lay their eggs in living wood, and their larvæ live for many years in the interior. They are to be met with in great numbers in forests of pine trees, and, according to Latreille, show themselves sometimes in such great numbers as to become an object of terror. The female of the Giant Sirex (_Sirex gigas_) possesses a long rectilinear auger. The mandibles of the larvæ are of great strength, and are even capable of perforating lead. This fact has been observed many times. In 1857 Marshal Vaillant presented to the Académie des Sciences some packets of cartridges containing balls which had been pierced through by the larvæ of the Sirex during the sojourn of the French troops in the Crimea. Some of these insects were still shut up in the gallery which they had hollowed out in the metal. M. Dumeril (and this was one of the last works of that venerable and learned naturalist) wrote a Report on this subject, in which were recorded many analogous instances. He quoted, as an example, that M. le Marquis de Brême, in 1844, showed to the Société Zoologique many cartridges in which the balls had been perforated by the insects to a depth of about a quarter of an inch. These cartridges came from the arsenal of Turin. They had been placed in barrels made of larch wood, the inside of which had been attacked by the insects. It was discovered that it was after having left the wood that they had gnawed through the envelopes of the cartridges, and at last into the balls themselves. In 1833 Audouin presented to the Société Entomologique de France a plate of lead, from the roof of a building, on which this naturalist supposed that the larvæ of a _Callidium_[107] had made deep sinuosities, as they do in wood. Before this, parts of the leaden roofs at La Rochelle had been noticed not only gnawed, but pierced from one side to the other, by the larvæ of _Bostrichus capucinus_.[108] In 1844 M. Desmarest reported the erosion and perforation of sheets of lead by a species of _Bostrichus_ and by _Callidium_. In 1843 M. Du Boys presented to the Société d'Agriculture of Limoges some stereotyped plates--composed, as is well-known, of a very hard alloy, formed of antimony and lead--which had been pierced and riddled with holes by two specimens of a _Bostrichus_. The holes were a seventh of an inch in diameter by two inches in depth. The stereotypes were thus perforated, although they had been wrapped up in many folds of paper and cardboard. As the printing served for a work called "Les Fastes Militaires de la France," one may say that the brave soldiers received from an insect more wounds than their enemies had ever given them.

[107] A coleopterous insect.--ED.

[108] Also a beetle.--ED.

To prove that these insects have really the power to perforate metals as others perforate and pass through woody matter, the entomologist of Limoges made the following experiments. He placed in a leaden box, the sides of which were thin, a living specimen of the Fire-coloured Lepture of Geoffroy (_Callidium sanguineum_), a Coleopteron which is commonly found in houses in France in winter, its larvæ being developed in great numbers in firewood. Above this box he fitted on another, also containing a specimen of this insect, which he shut in with a third box. A few days afterwards he separated the boxes. The middle one had been pierced through, and the two insects were found together, the one which was below having made a hole through which it might introduce itself into the middle box. M. Du Boys made a chemical experiment which enabled him to establish beyond a doubt that the insect which had gnawed the metal had not made it serve as its food. The dried body of one of these insects was analysed. After having immersed it in nitric acid it was completely burnt, and there could not be found in the ashes acted upon by the nitric acid the least trace of lead. This experiment proves that these insects had for their object only to escape from the galleries in which they were accidentally deposited in their larva state, and that it was not until they had undergone their complete transformation that they endeavoured to gain their liberty. Observations of the same kind were multiplied after the Report of M. Dumeril. The Académie des Sciences received, in the month of June, 1861, two Memoirs--one from M. Heriot, captain of artillery, the other from M. Bouteille, curator of the Museum of Natural History of Grenoble--containing many new observations on the perforation by insects of leaden balls contained in cartridges prepared for war. M. Milne-Edwards read to the Académie des Sciences a short Report on these works.

The insect which had produced the perforations observed in the balls sent to the Crimea in 1857, and which M. Dumeril particularly studied, was the _Sirex juvencus_, and had been taken from France in the wood forming the boxes which contained the cartridges. In the other case of which we are speaking, that is to say, of the cartridges which were sent in 1861 to the Académie by Captain Heriot and by M. Bouteille, the perforations had been produced by other species. M. Milne-Edwards, who found the insect that had caused this strange damage, had no trouble in recognising it as the _Sirex gigas_, which, in its larva state, lives in the interior of old trees or pieces of wood, and which, after it has gone through all its metamorphoses, comes out of its retreat to reproduce its kind. To clear themselves a passage, they cut away with their mandibles the ligneous substances or other hard bodies they meet with on their road. It was in pursuing this object that the insects, imprisoned accidentally in the packets of cartridges when they were yet only in the larva state, must have attacked the leaden balls, as also the paper and the other matters which they met with on their road, and which opposed their passage. M. Bouteille proves, in his Memoir, that M. Dumeril has committed an error in saying that the perforating organ employed by the _Sirex_ to attack the leaden balls in the cartridges in the Crimea was the auger situated at the extremity of the abdomen of the female, and intended for cutting into that part of the wood where it is to lay its eggs. M. Bouteille has established, in fact, that they were not only the females which attacked the cartridges, but that the males, which have no auger, had occasioned the same damage.

The _Tenthredinetæ_ are called "Saw-Flies," because the females are furnished with a double auger, notched like a saw, with which they cut into the branches in which they lay their eggs. The larvæ of these insects have a striking resemblance to the caterpillars of Lepidoptera. They can only be distinguished from them by a great globular head, not hollowed out, and by their abdominal legs, in general to the number of more than ten. They are called false caterpillars (Fig. 379). Most of them, when touched, erect themselves and move about in a threatening manner. They spin a silken cocoon before changing into pupæ. The _Lophyrus pini_, which devours the leaves of pine trees, belongs to this family.

VII.

THYSANOPTERA.

The very small black flies which are such a source of annoyance to travellers in the summer-time, and which fly into our eyes and crawl over our faces during the prevalence of warm windy weather, principally belong to a kind of insect which is characterised by having very remarkable wings when in the adult condition. These insects exist by myriads, and there are several species of them; and they are all exceedingly destructive to flowers, and especially to the bloom of cereal plants. The little black insects are to be seen on almost every flower, and they devour the delicate cellular tissues of the petals. _Thrips cerealium_ is very destructive when it occurs in multitudes upon the wheat, barley, and oats, for it interferes with the proper nutrition of the grain, by nibbling the protecting envelopes and the tissue which connects it to the stalk.

All the members of the genus _Thrips_--and they alone constitute the order now under consideration--possess four very narrow membranous wings, without any folds or network upon them, but furnished and decorated with beautiful fringes upon the edges. These fringes characterise the Order, which in other respects is closely allied to the Orthoptera, and they give the name to it. The Thysanoptera ([Greek: thysanoi], fringes; [Greek: pteron], a wing) have filiform antennæ and very large eyes, and the different species of the genus Thrips have a great diversity of wing fringing. The structure of the wings is somewhat analogous to that observed in the Lepidoptera, in the Pterophorina and the Alucitina.

The metamorphoses of the Thysanoptera have not received much attention, but they are known to be of the incomplete kind. The quiet chrysalis condition is not observed, and the larvæ are born from the egg greatly resembling the adults. The absence of wings is the great distinction between the larval and the imago state, as it is in the closely-allied order of the Orthoptera. The larva moults several times, and the wings are gradually added, the colour of the insect altering also.

VIII.

NEUROPTERA.

The Neuroptera--the type of which order are the _Libellulæ_, or Dragon Flies--have four membranous wings, generally rather broad, provided with transverse delicately reticulated nervures, which gives them the appearance of lace. Although one of the least extensive, this Order presents the greatest modifications of form and of habits.

One section of Neuroptera contains some insects which undergo incomplete metamorphoses. The _Libellulæ_, the _Ephemeræ_, and the _Termites_, belong to this category. The insects belonging to the other section, in which are classed the _Phryganidæ_,[109] or Caddis Flies, the _Panorpatæ_, and the _Myrmelionides_, or Ant Lions, undergo complete metamorphoses. The pupæ of the first walk and live absolutely in the same way as the larvæ; only, at the moment of the last transformation, the skin of the pupa splits, and the perfect insect comes forth. In the case of the second, on the contrary, the pupa is motionless, inactive, and takes no food, as in the Hymenoptera, Coleoptera, &c. In spite of this diversity in their mode of development, all these insects resemble each other too much for us to divide the Order; from which it follows that we must not attach too much importance to differences of transformation by which the insect arrives at its perfect state.

[109] These were separated from the Neuroptera and made a separate order, under the name of Trichoptera, by Kirby.--ED.

The most interesting insects among the Neuroptera are the _Termites_, improperly called White Ants, on account of the great analogy which exists between their habits and those of ants. They constitute, by their way of living, a striking anomaly in the order in which their conformation places them. In fact, they live in very numerous societies, and build very solid and very extensive dwelling-places--quite Cyclopean or Titanic works in comparison to the tiny dimensions and weak and feeble appearance of the insect. (PLATE IX.)

Many travellers have spoken of these insects. They are met with in the savannahs of North America, in Guyana, in Africa, in New Holland, and even in Europe, whither they have been imported. M. de Prefontaine relates that, when he was travelling in Guyana, he saw the negroes besieging certain strange buildings, which he calls ant-hills. They dared not attack them, except from a distance, and with fire-arms, although they had taken the precaution of digging all round them a little fosse filled with water, in which the besieged would be drowned if they made a sortie. These were the termites' nests.

Perhaps it is to termites Herodotus alludes when he speaks of ants which inhabit Bactria, and which, larger than a fox, eat a pound of meat a day.[110] Retired in the sandy deserts, these gigantic insects hollow out (says he) subterranean dwellings, and raise mounds of golden sand, which the Indians carry away at the peril of their lives. Pliny, who relates the same fables, adds that there were to be seen in the Temple of Hercules the horns of these ants. Even in our own days some travellers have repeated absurd fables about termites. They have attributed to them a venom which one cannot breathe without being poisoned; they have said that a single bite was enough to cause a mortal fever. The truth, as it is revealed to us by conscientious observers, is still stranger than these fictions or errors. The termites present curious modifications, on the nature of which naturalists are not agreed. There are, in the first place, the perfect insects, males and females, which are provided with wings; then there are the neuters, which are divided into _soldiers_, whose duty it is to defend the nest, and into _workers_, upon whom devolve the architectural works and household cares. These last are smaller than the soldiers. Latreille and some other naturalists think that these workers are the larvæ of the termites. Smeathman thinks that the soldiers are the pupæ. M. de Quatrefages admits that the soldiers are the neuters, and that the workers are recruited both from the larvæ and from the pupæ. It may be admitted, with other naturalists, that the soldiers and the workers are neuters: the first, abortive males; the second, abortive females. Here is, indeed, what M. Lespès has observed in the termites of the Landes. Among these insects, the most numerous are the workers: their size is that of a large ant, and their duties are to excavate galleries, to search for provisions, and to take care of the eggs, the larvæ, and the pupæ. The workers have a rounded head and short mandibles, and are blind. The soldiers, less numerous, have an enormous head--nearly as big as the rest of their body--very strong, crossed mandibles, and are blind like the workers. Anatomy showed M. Lespès that both are _neuters_--that is, the soldiers, males, and the workers, females--with aborted organs.

[110] De Quatrefages, "Souvenirs d'un Naturaliste," tome ii., p. 377. In 18mo. Paris, 1854.

The larvæ of the females much resemble the workers. Those which are to become males or females are distinguished from those which are to become neuters by very slight rudiments of wings, and their pupæ show already imperfect wings, hidden in cases; furthermore, they have eyes hidden under the skin. The males and females alone have eyes; they also have wings, which they lose immediately after the coupling. Those which proceed from the pupæ with long wing cases become small kings and queens after their swarming, which takes place at the end of May. The pupæ with short wing-cases become perfect in the month of August, and produce larger males and females, which become kings and queens. All these couples are collected by the neuters; and the queens, large and small, set to work immediately to lay. The largest are much the more fruitful. The workers do not seem to take any care of them at all. With the exception of this last peculiarity, everything probably goes on in the same manner with the exotic termites; but with the latter the queen is an object of worship.

Fig. 383 represents the four types of the republic of the _Termes lucifugus_. On the left is a worker, on the right a soldier, in the centre a winged male, all three very much magnified, the lines drawn by their side showing the natural size. Below the male is the pregnant queen (D D D D), of a species of which we are about to speak, of the natural size.

Many species of termites were studied with care by the English traveller, Smeathman, at the end of the last century, in Southern Africa. His account of them is the most exact and most complete which we have of these insects.[111] The largest of the species observed is the _Termes bellicosus_. The workers are a fifth of an inch long, the body soft, and of an extreme delicacy, but the sharp mandibles capable of attacking the hardest bodies. The soldiers are twice as long, and weigh as much as fifteen workers, and may be distinguished by their enormous horned head, armed with sharp pincers. The male weighs as much as thirty workers, and attains to a length of nearly four-fifths of an inch.

[111] "Some Account of the Termites," &c., in the _Philosophical Transactions_, vol. lxxi. 1781.