Some observations of Mr. Rennie show, in a singular manner, the fact before mentioned, that if the wings, while yet wet and soft, are in any way pressed upon, or otherwise injured, they will never assume their proper appearance. "The thread by which a chrysalis is suspended may sometimes snap asunder; when this happens, and the chrysalis is allowed to remain, it will not usually produce an insect complete in all its parts; for the side upon which it lies being pressed against an unyielding substance by its own weight, instead of hanging lightly suspended by a silken cord, is prevented from becoming duly expanded, and when the insect is excluded, it is found to be deformed. A colony of the brown-tail moth, which we reared during the summer of 1829, spun in the corner of a nurse-box, a common web of several chambers for containing the pupæ. One of these chambers being accidentally torn, a pupa fell upon the earth in the bottom of the box, and in due time, a female moth was produced from it; but she never succeeded in expanding her wings, which remained till her death, shrunk, rumpled, and totally useless for the purpose of flying, though in every other respect she was full grown, and deposited in the box a group of fertile eggs, covered with down from her tail, as neatly as was done by her sisters of the same brood. In the summer of 1825, the chrysalis of a small tortoise-shell butterfly, (Vanessa urticæ,) lost its hold of its silken suspensory, and fell upon the pasteboard bottom of a nurse-box, resting in a sort of angular position, so that the case of the upper wing on the left side, pressed upon the box with the whole weight of the chrysalis above it. When the butterfly made its appearance, it expanded its wings as usual; but the wing upon which it had rested was not half the size of the one on the right side which had lain uppermost. Another of the same brood had, from some cause, not grown so large in the caterpillar state as the rest. It was transformed, notwithstanding, into a chrysalis, which appeared healthy and well-formed; but when the butterfly appeared, though it did not differ from the usual appearance, its wings never expanded a single hair's breadth, and remained always in the same state as when it issued from the chrysalis."
After the insect has once withdrawn itself from the pupa-case, it generally retains the same appearance and raiment as long as it lives, not casting its skin like the larva, but having put on its permanent clothing immediately upon its leaving the pupa-case. But in the case of an aquatic insect, the Ephemera, of which we have before spoken, a remarkable exception to this rule has been noticed. When these insects leave the pupa-case, any one, on looking at them, would say that they had completed their changes; they appear to be furnished with every part necessary to them, and not to have any which is redundant; yet they are destined to go through a change equivalent to that which has just taken place, if, indeed, it is not more apparently difficult than it, and that is,—they have to cast off their skin. That they should be able to withdraw from thence their head, their legs, their body, and their long tails, would be no great difficulty for us to comprehend, because numbers of insects at their escape from the pupa-case do more than this; but in their case we are presented with a more perplexing enigma. In the transformation of other insects, as we have already seen, and, indeed, in that of the insects before us, the wings are at first very soft and pliable, and therefore can be easily withdrawn from the cases in which they were contained. But in the Ephemera, the wings, after it has left the pupa-case, are fully developed and expanded, and seem to have acquired all their consistence, and to have become hard and inflexible. Moreover, its wings are so thin, that we can scarcely believe that they are in reality double; that is, that they are covered by an outside sheath; and it seems incomprehensible how, if such is the fact, the wings can be withdrawn from this case or sheath, when the only opening that can be discovered for that purpose, is a very minute hole near the spot where the wings take origin from the body of the insect. Let us now see how all these difficulties are overcome, and how the insect withdraws itself from this, as we might almost call it, second pupa-case.
Dance of the Ephemeræ.
The Ephemeræ, when they leave the water, rise high into the air, and wing their way perhaps far from the place of their birth. They may often be found wheeling over green fields, or wandering among the forest shades, far from the bubbling stream in whose waters so large a portion of their existence was spent; but more frequently they are to be found somewhere in the neighbourhood of the stream, enjoying an aërial dance. The feet of the insect are armed with hooks of great minuteness, and by their means the insect attaches itself to a suitable object, sometimes to a wall, sometimes to a twig, or to the trunk of a tree; it does not much matter where. Without at first making the least movement, the insect patiently abides the time when it must withdraw itself from its useless upper garment, and sometimes it has to wait a whole day in this position. The time arrived, the skin splits, and the body of the insect rises gradually out of it; but the difficulty is about the wings. Nevertheless, as we watch the insect, we shall find that it gradually draws them out of their delicate cases, and at length emerges, as perfect in beauty and form as before. The manner in which this is effected is as follows:—although the outer case of the wings is hard and rigid, yet the wings which it covers over are preserved in a soft and moist condition. In proportion, therefore, as the insect disengages itself from the anterior part of the skin, the inner or real wings become contracted, by a number of plaits, into a form nearly cylindrical, which readily admits of their being pulled through the openings lately mentioned; and as soon as the insect is released from its envelope, these plaits unfold, and the wings return to their former shape and dimensions. So exactly does this thin skin, thus cast off, fit all the parts of the insect's body, that it may often be mistaken for the insect itself, when it is found clinging to the place where it has gone through its changes.
Wingless Beetle.
Before we leave the subject of the wings, it must be mentioned that there are some insects which have none. The cut represents a beetle of this class.
If the reader will now take a peep into one of the nurse-boxes in which he may have been rearing butterflies from the pupæ, presuming that several of them have ere this burst from their cases, and are fluttering about anxious for liberty, he will generally detect upon the bottom or sides of the box one or two marks of a somewhat reddish colour; sometimes, indeed, they are very red. These spots are produced by the insect, which, on its emergence from the pupa, generally deposits a drop of fluid from its intestines. Almost all insects perform the same action at this period; but we may well remark with Réaumur, it could scarcely have been supposed, that the excrements of a butterfly should ever have filled the minds of a whole population with terror. Such has, however, been the case, and may, perhaps, yet be in districts where ignorance and superstition close the minds of the inhabitants against the truths of entomology. "Historians," says Réaumur, "tell us of showers of blood, as having been the cause of terror to nations, and considered as prophetic of fearful events, of the destruction of cities, and revolutions of kingdoms. At the beginning of the month of July, in the year 1608, one of these showers of blood was said to have fallen in the suburbs of Aix, and for some miles around. It turned out that the supposed drops of blood were in reality drops deposited by the butterflies. It is not improbable that other showers of blood recorded by historians, and taking place about the same period of the year, might be accounted for in the same natural and simple manner. Gregory of Tours relates that in the time of Childebert a shower of blood fell in different places in Paris, and particularly in a certain house situated in the territory of Senlis. Another was said to have fallen toward the end of June, in the reign of King Robert. In the year 1533, we are told by another author, a prodigious multitude of butterflies appeared throughout a great portion of Germany, sprinkling plants, leaves, buildings, clothes, and men, with bloody drops, as if it had rained blood."