Part 20
In 1858 M. Guérin-Méneville presented to the Académie des Sciences of Paris the first moths and the first eggs laid in France of the _Attacus Cynthia_. This able entomologist demonstrated very soon afterwards--1st, that the caterpillars of this insect can be reared in the open air, and with scarcely any cost for management; 2ndly, that it produces two crops a year in the climate of Paris and the north of France; 3rdly, that the cultivation of the Ailanthus, or the false Japan varnish tree, on which this insect lives, is easy even in the most sterile soil.
M. Guérin-Méneville showed still further that _ailantine_, the textile matter furnished by the cocoon of the Cynthia, is a sort of floss silk holding a middle place between wool and the silk of the mulberry-tree worm, and which, as it can be produced at scarcely any expense, would be very cheap, and would serve for the fabrication of what are called fancy stuffs, for which ordinary floss silk is now used. In 1862 M. Guérin-Méneville sent in a Report to the Minister of Agriculture on the progress of the cultivation of the Ailanthus, and of the breeding of the silkworm, which was reared in the open air on this tree. He mentions, in his Report, the rapid development of the cultivation of the tree in France, the great number of eggs of the Ailanthus silkworm sold, the foundation of a model silkworm nursery at Vincennes, and, this one great point gained, that they had found out the way of unwinding the silk from the cocoons of the _Cynthia_ in one unbroken and continuous thread.
Till then European industry had only succeeded in drawing from the cocoons of the Ailanthus silkworm a floss silk, composed of filaments more or less short, obtained by carding, and unable to produce, when twisted, anything better than floss, that is to say, refuse silk. It is to the Countess de Vernéde de Corneillan, on the one hand, and to Doctor Forgemot on the other, that the merit is due of having obtained an unbroken thread of silk from the cocoon of _Attacus Cynthia_.
A monograph on the Ailanthus silkworm appeared in 1866 under the title, "L'Ailante et son Bombyx, par Henri Givelet."[67] It is a complete account of all the results obtained up to the time, both as regards the rearing of the silkworm and also as regards the cultivation on a large scale of the Ailanthus, or false Japan varnish tree.[68]
[67] In 8vo, avec plans et planches coloriées. Paris, 1866.
[68] A work by M. Guérin-Méneville on the same subject, entitled, "Education des Vers à Soie de l'Ailante et du Ricin," in 12mo., Paris, 1860, may also be consulted.
[For a full account of successful experiments carried on in England, see Dr. Wallace's essay in _The Transactions of the Entomological Society of London_, 3rd series, vol. v., pt. 2; Longmans and Co.--ED.]
The Castor-oil Plant Silkworm (_Attacus_ [_Bombyx_] _ricini_) is a species very nearly akin to the Ailanthus worm, perhaps only a variety, and comes from India. The silk which it produces is very similar in every respect to that of the _Cynthia_. The rearing of this worm could never attain to any great importance in France, on account of the necessity there is of renewing the plantations of the castor-oil plant each year. It would, however, afford an additional source of income to the farmers in the south of France, who cultivate the castor-oil plant with a view to selling its seeds, which are much used in pharmacy.
Nearly allied to the genus _Attacus_, which furnishes us with all these precious auxiliaries to the mulberry silkworm, are a great number of other species, both indigenous to Europe and exotic, mostly remarkable for their great size, and a few of which are common in this country.
Fig. 229 is the largest European moth, but never found farther north than the latitude of Paris. Its wings are brown, waved, and variegated with grey. Each of them has a large black eye-shaped spot, surrounded by a tawny circle, surmounted by one white semicircle, and by another of a reddish hue, the whole completely enclosed in a black circle. "These moths," says Geoffroy, "are very large; they look as if they were covered with fur, and, when they fly, one is inclined to take them for birds."
_Saturnia pavonia-major_ comes from a very large caterpillar, which is of a beautiful green, with tubercles of turquoise blue, each of which is surmounted by seven stiff divergent hairs. This caterpillar lives principally upon the elm, but it feeds also upon the leaves of the pear, plum, and other trees. It spins a brown cocoon, formed of a coarse silk of great strength. It is not until the following spring that it becomes a moth.
The Emperor Moth (_Saturnia carpini_, Fig. 230) much resembles the above, except in size. This species is common in England, and its green larva, covered with black or pink warts, from which spring hairs, as in the last, is by no means rare on heath in the autumn. It also feeds on bramble and other plants.
Among the _Attaci_ foreign to Europe, we must mention _Atlas_ (Fig. 231), the expanse of whose wings exceeds four and a quarter inches. This magnificent moth, one of the largest known, comes from China.
The family _Bombycidæ_ comprises many species which we must not omit to mention.
The Lackey (_Bombyx neustria_) derives its name from the colour of the caterpillar, which has longitudinal lines of various colours, and a blue head. These caterpillars live together on a great number of our forest and garden trees, to which they do much damage. The moth (Fig. 232) has a brownish body, and wings of a more or less tawny yellow colour, with two darker lines on the front wings.
The Procession Moth (_Bombyx processionea_) is a small greyish moth, the caterpillars of which live in numerous troops on oak trees, and devour the leaves at the moment of their development. In the evening these caterpillars come out of their common nest, and form a sort of procession; hence their name Procession Moth. "I kept some for a little time in my house in the country," says Réaumur. "I brought an oak branch which was covered with them into my study, where I could much better follow the order and regularity of their march than I could have done in the woods. I was very much amused and pleased at watching them for many days. I hung the branch on which I had brought them against one of my window shutters. When the leaves were dried up, when they had become too hard for the jaws of the caterpillars, they tried to go and seek better food elsewhere. One set himself in motion, a second followed at his tail, a third followed this one, and so on. They began to defile and march up the shutter, but being so near to each other that the head of the second touched the tail of the first. The single file was throughout continuous; it formed a perfect string of caterpillars of about two feet in length, after which the line was doubled. There two caterpillars marched abreast, but as near the one which preceded them as those who were marching in single file were to each other. After a few rows of our processionists who were two abreast, came the rows of three abreast; after a few of these came those which were four abreast; then there were those of five, others of six, others of seven, others of eight caterpillars. This troop, so well marshalled, was led by the first. Did it halt, all the others halted; did it again begin to march, all the others set themselves in motion, and followed with the greatest precision.... That which went on in my study goes on every day in the woods where these caterpillars live.... When it is near sunset you may see one caterpillar coming out of any of the nests, by the opening which is at the top, which would hardly afford space for two to come out abreast. As soon as it has emerged from the nest, it is followed by many others in single file; when it has got about two feet from the nest, it makes a pause, during which those who are still in the nest continue to come out; they fall into their ranks, the battalion is formed; at last the leader sets off marching again, and all the others follow him. That which goes on in this nest takes place in all the neighbouring nests; all are evacuated at the same time."
One part of Fig. 233 shows the arrangement of the caterpillars on coming out of the nest. These caterpillars are furnished with long hairs, slightly tufted, which come off with the greatest ease, and which if they penetrate into the skin, cause violent itching. In 1865 a number of the alleys of the Bois de Boulogne were shut up from the public in order to save them from this annoyance. These caterpillars construct a covering common to them all, in which they live, and transform themselves therein, each insect making for his own private use a small cocoon. This insect is said to have been found in England, but there is not sufficient evidence to admit it into our lists.
The _Orgyias_ comprise a great number of small species, of a dark colour, which do a great deal of damage to our forest trees. In September and October the male of the _Orgyia antiqua_, with his tawny wings, may often be seen flying about the streets of London. The female (Fig. 234) is remarkable, as she has only the rudiments of wings, and only goes as far as the side of her cocoon. The caterpillar of the _Orgyia pudibunda_, called also the Hop Dog, attacks almost every sort of tree. When the state of the atmosphere favours their propagation, they appear in fearful quantities, and cause the greatest havoc. During the autumn of 1828, in the environs of Phalsbourg, they were to be counted by millions. The extent of the woods laid waste was calculated at about fifteen hundred hectares. It is common in this country.
Among the genus _Liparis_, the species of which are also very destructive to trees, we must mention the Brown-tailed Moth (_Liparis chrysorrhoea_, Fig. 236), a species by no means rare in England. The caterpillars live in quantities, on apple, pear, and elm trees, and destroy the plantations of the promenades of Paris.
The females of this genus tear off the fur from the extremity of their abdomens to make a soft bed for their eggs, and to preserve them from the cold. And yet they are never to see their young, for they die after they have laid their eggs. Another tribe of _Bombycina_ contains species of a small size, which are remarkable from the habits of their caterpillars, which make, with foreign bodies, cases, in the interior of which they live and undergo their metamorphoses.
The caterpillars of the genus _Psyche_ live in a case composed of fragments of leaves, of bits of grass and straw, of small sticks of wood, or of little stones, stuck together, and intermixed with silky threads.
We give a representation (in Figs. 237, 239, and 240) of the cases of the caterpillars of three different kinds. The females of these moths are completely destitute of wings, and resemble caterpillars. As a general rule they hardly ever leave their case. The males (Figs. 238, 242) are of a blackish grey, and fly very swiftly.
The caterpillars of the genus _Hepialus_ are difficult to observe, as they live in the interior of the roots of various vegetables. Such is the common Ghost Moth (_Hepialus humuli_), which sometimes causes the greatest damage.
The type of the genus _Zeuzera_ is _Zeuzera æsculi_, or Wood Leopard (Fig. 243). It has white wings with large blackish blue spots on the anterior, and small black spots on the posterior wings. The caterpillar, of a vivid yellow, spotted with black, lives in the interior of the trunks of a great many trees, principally the chestnut, the elm, the lime, and the pear tree. This moth, which is known also by the name of Coquette, is to be seen in the evening flying about the public gardens of Paris, and is not rare in England. The most celebrated species of the allied genus _Cossus_ is the Wood-boring Goat Moth (_Cossus ligniperda_), figured in the opposite plate. The moth has a heavy brownish body and greyish wings streaked with black. It is found in most parts of Europe. The caterpillar is of a reddish colour, as if it had on a leathern jerkin, and disgorges a liquid which is believed to soften ligneous fibres, and it lives in the interior of willows and other trees. It was on this caterpillar that Lyonnet made his admirable anatomical researches.
Another tribe of _Bombycina_ comprises some very strange caterpillars, whose hindermost feet are changed into forked prolongations, which they move about in a threatening manner. These sort of fly-traps are perhaps meant to keep at a distance those insects which would lay their eggs upon the caterpillar's body. The caterpillars of _Dicranura_ are of this kind. We give a representation of the caterpillar and the moth of the Puss Moth (_Dicranura vinula_, Figs. 244, 245), as also the moth of the _Dicranura verbasci_, the former of which is common in England, and the larva may be found during the late summer and early autumn feeding on poplars and willows; and of the caterpillar of _Stauropus fagi_, the Lobster Moth (Fig. 247), rare in France, whose appearance is strange indeed. The moths, on the contrary, have nothing about them remarkable.
The _Noctuina_ are a group of Lepidoptera of middling size, and generally found in woods, meadows, and gardens, where their caterpillars have lived. They seldom fly till about sunset, or during the night. Their upper wings are of a dark colour, with spots in the middle of a particular shape. Their lower wings are of various colours, often whitish, sometimes red or yellow.
We give representations of some of the species of this group.[69] _Noctua tegamon_, Fig. 248; _Noctua nebulosa_, Fig. 249; _Noctua musiva_, Fig. 250; _Noctua brunnea_, Fig. 251; _Catocala fraxini_, Fig. 252; _Catocala Americana_, Fig. 253; _Catocala paranympha_, Fig. 254; _Catocala nupta_, Fig. 255, the Red Underwing; and _Erebus strix_, Fig. 256.
[69] In England it numbers about three hundred species. The larvæ are of diverse habits, but the majority feed on low plants; the moths are provided with a trunk, and are very partial to sweets.--ED.
The bodies of these moths are robust and sometimes massive, and are scaly rather than woolly. The thorax is sometimes bristling with hairy tufts.
This genus includes 800 species, of which there are about 300 in France. The caterpillars of the _Noctuina_ are smooth or very slightly covered with hair, usually of a pale colour, and live on low plants, of which they devour, some the leaves, others the roots; then it is they are most destructive to agriculture. There are some of them which eat any caterpillars they may chance to meet, and even those of their own species, leaving nothing but the skin. Some of them surround themselves with a light cocoon before becoming chrysalides; others bury themselves in soft, well-pulverised soil.
The family of _Geometrinæ_, or Geometers, comprises moths of a middling size, and usually flying after sunset and during the night.[70] They frequent the alleys of damp woods, where they become the prey of the _Libellulæ_[71] and other carnivorous insects. Their bodies and abdomens are slender, their wings large, thin, fragile, often of a dark colour, with brilliant markings.
[70] few species fly in bright sunshine.--ED.
[71] Dragon-flies.--ED.
The caterpillars of the _Geometrinæ_ are known by the name of loopers or geometers. We have previously described their singular organisation. They are continually spinning a silken thread, which keeps them attached to the plant on which they live. If you touch the leaf which supports them they immediately let themselves fall.
"Nevertheless, they do not generally fall to the ground," says Réaumur; "there is a cord ready to support them in the air (Fig. 257), and a cord which they can lengthen as they will; this cord is only a very thin thread, but has nevertheless strength enough to support the caterpillar (Figs. 258, 259). All that there seems to fear is, that the thread may lengthen too quickly and the caterpillar fall, rather than descend gently, to the ground. But what we must first remark and admire is, that the caterpillar is mistress of its movements, and is not obliged to descend too quickly; it descends by stages; it stops in the air when it pleases. Generally it only descends at most about one foot at a time, and sometimes only half a foot or a few inches, after which it makes a pause more or less long, as it pleases." It is in this way that the caterpillars let themselves fall from the top of the highest trees: they remount again with no less ease.
Let us listen to Réaumur's description of the means employed by this caterpillar to ascend these heights. Figs. 260 and 261, drawn, as the three preceding ones, from the plates in Réaumur's Memoir, help us to follow the explanation given by the illustrious naturalist of the evolutions of our little acrobat:--"To remount," says Réaumur, "the caterpillar seizes the thread between its jaws, as high up as it can; as soon as it has done this it twists its head round, lays it over on one side, and continues to do so more and more every moment. Its head seems to descend below the last of the scaly legs which are on the same side as that to which it is inclined. The truth is, however, that it is not its head which descends, the part of the thread which it holds between its jaws is a fixed point for its head and for the rest of its body; it is that portion of the back corresponding with its scaly legs which the caterpillar twists upwards; the consequence is that the scaly legs and that part of the body to which they belong then ascend. When the last pair of legs is just over the jaws of the caterpillar, one leg, viz., that which is on the side towards which the head is inclined, seizes the thread and brings it over to the corresponding leg on the other side, which is advanced to receive it. If the head is then raised, which is done immediately, it is in order that it may seize the thread at a higher point than that at which it was caught at first; or, which is the same thing, the head, and consequently the whole body of the caterpillar, is found to have ascended to a height equal to the length of the thread which is between the place where its jaws seized it the first time and that where they seized it the second time. The first move in the upward direction is thus made, and the second soon follows.... If you were to seize the caterpillar on its arrival at the end of its upward journey, you would see a packet of threads huddled together between the four hindmost of the scaly legs. The greater the height ascended the greater is the size of this packet. All the turns of the thread which compose it are entangled. So the caterpillar does not consider it of any value. As soon as the insect can walk it gets rid of the mass, sets its legs free, and leaves it behind before one or at most two steps have been taken. The cord is wasted on each ascent, but the caterpillar can afford to lose as many as it likes, for it has in itself the source of the matter necessary for the composition of the thread, and it is a source from which that which was drawn off is being continually re-supplied. Moreover, spinning the thread costs the caterpillars but little; indeed, the loopers economise this thread so badly that most of them leave it behind them wherever they go."
They are found on many trees, but particularly on the oak, the foliage of which they often entirely devour. They burrow into the ground to change into chrysalides, and undergo all their metamorphoses in the course of the year. Others do not become perfect insects till the autumn, or sometimes not even till the following spring. A few assume the perfect state in winter. There are, indeed, some of these, such as the males of the _Hybernias_, which fly about on the foggy evenings of November. The females of this genus have either no wings at all, or else only rudimentary ones. Two species, the _Hybernia defoliaria_, or Winter Moth, and the _Chimatobia brumata_, abundant here, are very common in the environs of Paris.
M. Maurice Girard says, in his work on the metamorphoses of insects, that the females of these moths can easily be found at the beginning of November, in a very strange place, namely, on the gas lamps of the public promenades; for instance, along the roads in the Bois de Boulogne. No doubt they had climbed up to this height, attracted by the light, or perhaps had been carried thither by the males, which fly, having wings.
In February and March appear other analogous species. "We may find," says M. Maurice Girard, "near Paris, in the meadows which surround the confluence of the Seine and the Marne, at the end of the month of March, the _Nyssia zonaria_ (Fig. 267), the males of which insect remain during the day motionless on the grass."[72]
[72] With us this insect has a very limited range, being only found at New Brighton, near Birkenhead, where it is most abundant.--ED.
There are some species of this family in which the wings of the females are developed like those of the males.[73] Such are the Peppered Moth (_Amphidasis betularia_) and the Currant Moth (_Abraxas grossulariata_), whose caterpillar lives on the red currant and gooseberry, and an immense number known as Thorns, Carpets, Waves, &c.
[73] The exception is with those in which the wings are _not_ developed in both cases, and in England this peculiarity is confined to species appearing during the winter and early spring.--ED.
The section of the _Pyralina_ contains the smallest nocturnal Lepidoptera, and nearly all those tiny species which flutter round our lights in the evening.