Part 10
never dreamt of such victuals, for it lives entirely on the sap of large vegetables. The fables of the poet, who is called in France, one never knows why, "Le bon La Fontaine," teem with errors of the same kind as those we have just pointed out. The habits of animals are nearly always represented as exactly the contrary to what they really are. To initiate himself into the mysteries of the habits of animals, La Fontaine certainly had neither the works of Buffon nor the memoirs of Réaumur, which had not then been written; but had he not the book of Nature?
But it is time to mention the principal species of the Cicada. We will describe two: that of the Ash, which lives on those trees in the south of France; and that of the Manna Ash, which is very common in the south-east of France. It is particularly plentiful in the forests of pines which abound between Bayonne and Bordeaux. It is on these two species of Cicada that Réaumur made the beautiful observations of which we gave a summary above.
The _Cicada plebeia_ or _Tettigonia fraxini_, very common in Provence, is found, though rarely, in the forest of Fontainebleau, occasionally in La Brie. It is of a grey yellow below, black above; the head and thorax are marked or striped with black.
M. Solier, in a Memoir inserted in the "Annales de la Société Entomologique de France," says that its song, very loud and very piercing, seems to consist of one single note, repeated with rapidity, which insensibly grows weaker after a certain time, and terminates in a kind of whistle, which can be partly imitated by pronouncing the two consonants _st_, and which resembles the noise of the air coming out of a little opening in a compressed bladder. When the Cicada sings, it moves its abdomen violently, in such a manner as alternately to move it away from, and to bring it near to, the little covers of the sonorous cavities; to this movement is added a slight trembling of the mesothorax.
The same entomologist relates a very interesting observation made on this species of Cicada by his friend, M. Boyer, a chemist at Aix, and which he himself verified. The Cicadas, in general, are very timid, and fly away at the least noise. However, when a Cicada is singing, one can approach it, whistling the while in a quavering manner, and imitating as nearly as possible, its cry, but in such a manner as to predominate over it. The insect then descends a small space down the tree, as if to approach the whistler; then it stops. But if one presents a stick to it, continuing to whistle, the Cicada settles on it and begins again to descend backwards. From time to time it stops, as if to listen. At last, attracted, and, as it were, fascinated by the harmony of the whistle, it comes to the observer himself.
M. Boyer managed thus to make a Cicada, which continued to sing as long as he whistled in harmony with it, settle on his nose. Charmed by this concert, the insect seemed to have lost its natural timidity.
The _Cicada orni_ is of a greenish yellow, spotted with black. The abdomen is encircled by the same colours. The elytra and the wings are hyaline, or glassy, and their veins alternately yellow and brown. The legs are yellow throughout. The song of this species is hoarse, and cannot be heard at any great distance.
M. Solier, in the work we quoted just now, says that the song of this Cicada is of a deeper intonation, but that it is quick and is sooner over. It does not terminate in the manner which characterises that of the other species.
Next the genus _Cicada_ comes _Fulgora_, whose type is the _Fulgora lanternaria_, or Lantern Fly (Fig. 83).
Belonging to South America, these insects are above all remarkable and easy to recognise, by their very large elongated head, which nearly equals three-quarters of the rest of the body. This prolongation is horizontal, vesiculous, enlarged to about the same breadth as the head, and presents above a very great gibbosity. The antennæ are short, with a globular second articulation, and a small terminal hair. The species represented in Fig. 83 is yellow varied with black. The elytra are of a greenish yellow, sprinkled with black; the wings, of the same colour, have at the extremity a large spot resembling an eye, which is surrounded by a brown circle very broad in front. It inhabits Guyana. This remarkable insect enjoys a great renown with the vulgar, by a peculiarity which might be called its speciality--the property of shining by night or in the dark. Hence its name of _Fulgora lanternaria_.
The knowledge of the _Fulgora lanternaria_ has been spread and popularised in Europe by a celebrated book, which has for its title, "Métamorphoses des Insectes de Surinam." This book, which contains the result of patient study of the natural history of Dutch Guyana (Government of Surinam), was written and published in three languages, by a woman whose name this work has rendered immortal--Mlle. Sybille de Mérian--and who won the admiration and respect of her contemporaries by her love of the beauties of Nature, and her perseverance in making them known and admired. Sybille de Mérian was born at Bâle. Daughter, sister, and mother of celebrated engravers, herself an excellent flower-painter, she had worked a long time at Frankfort and at Nuremburg; and had read with the greatest attention the "Théologie des Insectes,"[25] and with admiration Malpighi's book on the silkworm. Full of enthusiasm for the study of natural history, she left Germany, to visit the magnificent collection of plants which were kept in the hot-houses of Holland, and made admirable reproductions of them with her pencil.
[25] "Théologie des Insectes, ou Démonstration des Perfections de Dieu dans tout ce qui concerne les Insectes, par Lesser, traduit en Français." La Haye, 1742.
This attentive study of the vegetable world suggested to her the idea, which soon became an ardent desire, of observing these marvels of Nature in those parts of the globe in which they display themselves with the greatest magnificence and splendour. At the age of fifty-four, Sybille de Mérian set out for equatorial America. From the very first days of her arrival she hazarded her life, sometimes without a guide, in the swampy plains or burning valleys of Guyana. During the two years she sojourned in those dangerous parts, she made a large collection of drawings and paintings, which were destined to inaugurate in Europe the introduction of art into natural history.
In the plates to her work, Sybille de Mérian represents always the insects she wishes to describe under its three forms of larva, pupa, and perfect insect. With this drawing she gives another of the plants which serves the insect for food, as also of the animals which prey on it. Each plate is a little drama. Near the insect is seen the greedy lizard opening its dreadful mouth, or the ferocious spider watching for it. The short life of insects is shown here in its entirety, with its continual struggles, its infinite artifices, its rapid end, and all the episodes of its existence, for which life, as in the case of the moral man, is but a long and painful struggle.
Such was the work, such was the noble devotion and the worthy career of Sybille de Mérian. Let women, let young girls, who are martyrs to the ennui of a life devoid of occupation, peruse her beautiful books, and learn from it how much a woman may do with the time which is now either utterly unoccupied or only devoted to useless employments. To study Nature in any of its phases ought, it seems to us, to give more satisfaction to the soul, more strength to the mind, and cause more admiration of and gratitude to the supreme Author of Nature than doing a little embroidery.
It is, as we have already said, in the work of Sybille de Mérian, "Métamorphoses des Insectes de Surinam," that one finds mentioned, for the first time, the luminous properties of the _Fulgora lanternaria_. The author thus relates her observations, which were the result of chance:--
"Some Indians having one day brought me a great number of the Lantern Flies, I shut them up in a large box, not knowing then that they gave light at night. Hearing a noise, I sprang out of bed and had a candle brought. I very soon discovered that the noise proceeded from the box, which I hurriedly opened; but, alarmed at seeing emerging from it a flame, or, to speak more correctly, as many flames as there were insects, I at first let it fall. Having recovered from my astonishment, or rather from my fright, I caught all my insects again, and admired this singular property of theirs."
Since the time when Mlle. de Mérian visited Guyana, different travellers have said that they could not observe, as she did, this phosphorescent phenomenon. It is, then, probable that this property only exists in the male or female insect, and then only at certain seasons.
What a marvellous spectacle must the rich valleys of Guyana present, when, in the stillness of the night, the air is filled with living torches; when, the _Fulgoræ_ flying about in space, the flashes of fire cross each other, go out and blaze up again, shine brightly and then die out, and present, on a calm evening, the appearance of those lightning flashes which are usually seen only in the midst of a tempest!
Let us now go on to another interesting insect of the order of which we are treating, the Aphrophora, without being frightened by its disagreeable name, for there are many other names we may give it if we choose among those by which it is popularly known. In the months of June and July one sees on nearly every tree, and on plants of the most different kinds, a sort of white froth, composed of air bubbles, deposited on the leaves and branches. It is produced by an insect which the peasants in France call _Crachat de Coucou_, or _Ecume printanière_ (spring froth), and which is called in England, Cuckoo's spittle. De Geer carefully studied the metamorphoses of this insect. The Aphrophora (from [Greek: aphros], foam, and [Greek: pherô], I bear or carry) is lodged in the froth of which we have just been speaking. It lives in it, only leaving it when it has its wings. De Geer wondered why this insect confines itself during the whole of its life in liquid, and concludes that the froth has the effect of protecting the insect from the burning heat of the sun. This covering seems also to protect it from the attacks of carnivorous insects and spiders. On the other hand, its skin is without doubt so constituted that it would perspire too freely if it were exposed to the air, and the insect would very soon die dried up. Whatever explanation may be given of the necessity for this semi-aërial, semi-liquid medium, it is easy to verify the fact that the larva of the Aphrophora cannot live long out of its frothy envelope. If withdrawn from it, the volume of its body diminishes perceptibly, and the poor animal dies, like a fish taken out of its natural element.
The insects which live in this froth are six-legged grubs (Fig. 84), which, when the froth is cleared from them, walk quickly enough on the stalks and leaves of plants. They are green, with the belly yellow.
De Geer wished to know how they produced this singular froth, and found out in the following manner:--He took one of them out of its frothy dwelling, wiped it dry with a camel's-hair pencil, and placed it on a young stalk, recently cut from the honeysuckle, which he put into water in a glass, in order to preserve its freshness, and this is what he observed:--
"It begins," says the Swedish naturalist, "by fixing itself on a certain part of the stalk, in which it inserts the end of its trunk, and remains thus for a long time in the same attitude, occupied in sucking and filling itself with the sap. Having then withdrawn its trunk, it remains there, or else places itself on a leaf, where, after different reiterated movements of its abdomen, which it raises or lowers and turns on all sides, one may see coming out of the hinder part of its body a little ball of liquid, which it causes to slip along, bending it under its body. Beginning the same movements again, it is not long in producing a second globule of liquid, filled with air like the first, which it places side by side with, and close to, the preceding one, and continues the same operation as long as there remains any sap in its body. It is very soon covered with a number of small globules, which, coming out of its body one after the other, tend towards the front part, aided in this by the movement of the abdomen. It is all these globules collected together which form a white and extremely fine froth whose viscosity keeps the air shut up in the globules, and prevents its froth from easily evaporating. If the sap which the larva has drawn from the plant is exhausted before it feels itself sufficiently covered with froth, it begins to suck afresh, until it has got a new and sufficient quantity of froth, which it takes care to add to its first stock."[26]
[26] "Mémoires pour servir à l'Histoire des Insectes," tome iii.
It is in the froth that the larvæ change into pupæ, and they do not leave their habitation to undergo their final metamorphosis. They have then, says De Geer, the art of causing the froth inside to evaporate and dry up, in such a manner as to form a space inside the mass of froth, in which their bodies are entirely free. The exterior froth forms a roof closed in on all sides, under which the insect lies quite dry.
In this vaulted cell the pupa disengages itself little by little from its skin, which first splits up along the head, and then on the thorax. This opening is sufficiently large to enable it to come out of its envelope. It is in the month of September that these insects are particularly abundant, and then the trees and plants are covered with them. Sometimes the froth drips off, like a sort of small rain, from branches which are covered with it. Towards the autumn the females are pregnant. They are then so heavy that they can hardly jump or fly. The males, on the contrary, make prodigious bounds; they throw themselves forward to a distance of more than two yards. They are very difficult to catch, and still more difficult to find again when one has once let them escape. And so Swammerdam calls these insects _Sauterelles-Puces_ (Flea-Grasshoppers), because they jump like fleas.
All that we have said relates to the _Aphrophora spumaria_, or Froghopper (Fig. 85), an insect common all over Europe, and which Geoffroy calls the _Cigale bedeaude_.
"It is of a brown colour," says Geoffroy, "often rather greenish. Its head, its thorax, and its elytra, are finely dotted; on these last one sees two white oblong spots. The lower part of the insect is light brown."[27]
[27] "Histoire abrégée des Insectes, dans laquelle ces animaux sont rangés dans un ordre méthodique." In 4to. Tome i., p. 416. An VII. de la République.
We will mention, as it belongs to the group with which we are now occupied, a noxious insect, _Iassus devastans_, which since 1844 seems to have taken up its quarters in the commune of Saint Paul, in the department of the Basses-Alpes. It sucks the leaves and stalks of cereals, causing them to wither, and may be found even in winter on young corn, but principally in the spring. According to M. Guérin-Méneville, its head is of an ochrey yellow, with the apex marked with black spots; the forehead yellow, elongated, striped with black, as are the legs. The elytra are straw-coloured and spotted with brown. The wings are transparent, and slightly blackened at the extremities. This remarkable insect, which is not more than the twelfth of an inch in length, jumps and flies with great ease.
A small brownish insect, whose strange appearance struck Geoffroy, the historian of the insects of the environs of Paris, may be seen springing over the fern stalks and thistles, in the damp parts of most of the woods of Europe.
Geoffroy calls this insect "le Petit Diable." "Le Petit Diable," he writes, "is of a dark blackish-brown. Its head is flat, projecting but slightly, and, as it were, bent downwards. Its thorax, which is rather broad, has two sharp horns, which terminate in pretty long points on the sides. In the middle of the thorax is a crest or comb, which, prolonged into a sort of sinuous and crooked horn, terminates in a very sharp point, reaching to within one quarter of the extremity of the wing-cases. These--viz., the wing-cases--are dark, with brown veins; and the wings, shorter than their cases, are rather transparent. The insect jumps very well, and is not readily caught."[28]
[28] "Histoire abrégée des Insectes, dans laquelle ces animaux sont rangés dans un ordre méthodique." In 4to. Tome i., p. 423. An VII. de la République.
The Petit Diable of Geoffroy is the _Centrotus cornutus_ of modern naturalists. This curious little insect belongs to a strange and remarkable group, whose thorax takes the most extraordinary and most varied forms, as may be seen in Fig. 86, which represents somewhat magnified, many of these insects. Nearly all inhabit Guyana, the Brazils, and Florida.
We will now proceed to examine one of the most interesting groups of insects--that of the Plant-lice. These insects have for a long time attracted the attention of naturalists. They are so abundant that all our readers have seen them, and there are few plants in our fields or gardens which do not nourish some species. How often does one hesitate in gathering a rose or a bit of honeysuckle, for fear of touching the unattractive guest of those charming flowers!
During the whole of the summer one sees on the branches, on the leaves, but principally on the young shoots of the rose-tree, large companies of green plant-lice, which subsist on the sap of the tree. Some are provided with wings (Figs. 87, 88), others are wingless (Figs. 89, 90). The last-named are the largest, and are a line and a half long. They are entirely green, except two parts, of which we will speak immediately. The body is oval; the head is small, and furnished with two brown eyes. The skin is smooth, and tightly drawn over the body. The antennæ, which are very long and slender, almost equal the body in length. The six legs are long and slim, and the short feet terminate in two hooks. On the upper part of the body are two small cylindrical horns, surmounted by a small knob. The antennæ and these horns are black.
The winged individuals are of the same size as these, but are of a dark green colour, mixed with black. The wings are transparent, and the upper ones are as long again as the body. The young shoots of the elder-tree, all round their circumference for the length of from a foot to a foot and a half, are often covered with black plant-lice, or with those of a greenish-black colour. They are crowded one against the other, and sometimes there are two layers of them.
If observed without moving the plant about, they appear to be tranquil and inactive. They are, however, then absorbing from the plant the nourishment it should have; piercing with the point of their trunks the epidermis of the leaves or stalks, and drawing from them a nourishing liquid.
But this occupation is confined to those which are on the plant itself. Those which, on account of the enormous agglomeration of these insects, walk, not on the branch, but on other plant-lice, and cannot therefore suck the sap of the plant, are employed entirely in preserving and multiplying their species.
Réaumur often saw the latter, easily recognised by their great size, giving birth to little plant-lice, which are quite alive when they leave their mother. The young ones set off and mount or descend till they reach one end of the crowd, and there each takes up its position, like a cardboard capuchin (_capucin de carte_), in such a manner that the head is just behind the plant-louse which precedes it. There they bury their trunks in the vegetable tissue, and set to work to imbibe the sap.
Small as is the trunk of the plant-louse, yet when there are thousands of those little beings fixed to the stalk or the leaves of a plant, it is evident that it must suffer. And so the plant-louse is, in truth, one of the most terrible enemies of our agricultural and horticultural productions, and the exact list of the ravages which it occasions would be indeed interminable. We will confine ourselves to a few examples. For some years the lime-tree aphis has seriously attacked the lime-trees of the public promenades of Paris. The peach-tree plant-louse causes the blight of the leaves of that tree. It is to these prolific little parasites that are due, in a great number of cases, the contortions of leaves and of the young shoots of trees of all sorts.
These insatiable depredators cause sometimes a still more remarkable alteration. On the leaves of elms are often seen bladders round and rosy, like little apples. On opening these bladders one finds that they are inhabited by a species of aphis. On the black poplar galls of different kinds grow, some from the leaf stalks, and others from the young stems. They are rounded, oblong, horned, and twisted into a spiral. Other galls show themselves on the leaf itself. They are all inhabited by plant-lice, differing from those of which we have given a description above, in the extremity of their abdomen not presenting the two remarkable horns to which we shall have later to call the attention of the reader. The body is generally covered with a long and thick down.
Of this genus, the species, alas! so unfortunately celebrated is the Apple-tree Aphis (_Myzoxyle mali_), which attacks that tree. This insect is of a dark russet brown, with the upper part of the abdomen covered with very long white down. Its presence was announced for the first time in England in 1789, and in France, in the department of the Côtes du Nord, in 1812. In 1818 it was found in Paris, in the garden of the École de Pharmacie. It had become common in 1822 in the departments of the Seine, the Somme, and the Aisne. In 1827 its presence in Belgium was announced.
The apple-tree aphis, according to M. Blot, can only exist on that tree. Carried away and placed on any other, it very soon perishes. It does not attack the blossom, the fruit, nor the leaves, but fixes itself on the lower part of the trunk, whence it propagates itself downwards as far as the roots, underneath the graftings, &c. It also likes to lodge in cracks of the trunk and large branches. But it always looks out for a southern, and avoids a northern aspect. It is not active, walks very little, and its dissemination from one place to another can only be explained by the facility with which so small an insect can be transported by the wind, its lightness being still more increased by the down which covers it.
The _Myzoxyle mali_ renders the wood knotty, dry, hard, brittle, and brings on rapidly all the symptoms which characterise old age and decay in attacked trees. M. Blot recommends the following means for preserving the apple-tree from this insect: Employ for the seed-beds the pips of bitter apples only; give to the nursery and to the plants only as much shelter as is absolutely necessary; avoid those sites which are too low and too damp; encourage the circulation of air, and the desiccation of the soil; surround the foot of each apple-tree with a mixture of soot or of tobacco and fine sand.