Butterflies and Moths (British). Furneaux William Samuel
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persistently, as if to work their bodies into some shady corner. I would not advise a young entomologist to try this experiment, however, if he values the pupæ he possesses, for direct sunlight is undoubtedly very harmful to many species, and perhaps it is to all.
Some chrysalides are not nearly so active as has just been represented; in fact, there are many which seem to show no signs of life during the greater part of the time spent in that state. But in all, whether apparently active or not, certain important internal changes are at work. We have already noticed that, even in the last days of the larval existence, some of the organs of the future imago are to be traced. But these are as yet imperfectly developed. We have also observed that a continuation of these changes, gradually carried on, would be impossible in a voracious feeder; so the insect, now fully grown, and no longer requiring a supply of food, settles down in perfect quiet, submitting itself quite passively to any further changes that nature may demand.
It has already suffered the loss of its claspers. Its wonderful jaws that did so much damage (for good or evil as the case may be) to the vegetable world are now gone, and the bulky digestive apparatus has rapidly dwindled to useless dimensions. These and other changes, already in progress, have to be perfected while the creature is in a restful and helpless condition, though they may often be retarded or even suspended during cold weather when progress would certainly bring it to an untimely end.
But now the grandest of all these transformation scenes is nigh at hand. The protective skin is already loosening from the almost perfect imago, and consequently feels softer and far more yielding than it did when in close contact with the body: the swaddled butterfly or moth (for such the pupa is) is slowly preparing to throw off its imprisoning garb. The wings and large compound eyes are assuming their final colours, which now begin to show themselves through the more or less transparent skin, and the long legs, the perfectly formed antennæ, and the slender proboscis, all of which are folded closely under the creature's thorax, now begin to move within their loosened sheaths.
Now let us watch it closely, for one of the most wonderful sights ever witnessed by a naturalist is about to be presented to our view. We think we can observe slight movements; and, it may be, we can actually see the struggling insect endeavouring to set itself free. The legs and proboscis are moving within the loosened skin; and lo! as we watch these motions, the prison wall bursts with a slight snapping noise (at least, such is the case with some of the larger species), and in a moment out pop a few long legs which immediately struggle for a foothold. The proboscis also appears, alternately lengthening itself out and coiling into a spiral, as if impatient to reach the sweet nectar from the bottom of some fragrant flower cup.
Fig. 36 – A Butterfly, just after Emerging.
All this takes place in less time than one requires to describe it; and, before many seconds have passed, the struggling insect has quite completed its last moult, and is bidding good-bye to the rent garment that has done it good service for so long a time.
But how dreadfully disappointing! Did we not say only a few minutes since, that a beautiful butterfly or moth was about to emerge? How, then, is this? Here is an odd-looking creature, such as we have never seen before! True, it has the right kind of body, though even that is so soft and heavy that it is fairly dragged along as the insect walks. Its antennæ, too, seem to be just the right thing – that is, just what we were expecting to see. But oh! the wings! Are we looking at a deformity? – a failure on the part of Nature to produce what she ought?
We will not judge hastily, but continue to watch it a little longer. It seems very restless at first, and, with the fluttering apologies for wings, drags its heavy body along till it reaches some surface up which it can climb. If nothing of the kind is close at hand you may place a rough upright stick in its path, and it will immediately begin to ascend. Its motto is now 'Excelsior!' and its ambition to rise may be so great that, on reaching the very top of the stick provided for it, it struggles for a still higher position in life till, failing to get a foothold in the air itself, it falls to the ground and has to retrace its steps.
I once thought I would like to test the perseverance of a large moth in performing its first upward journey; and as it was one from a chrysalis to be found in nature at the foot of a tree that attains some considerable height, I was, of course, prepared to exercise a little patience myself.
As soon as the moth had emerged, I placed it at the bottom of a window curtain that hung from about eight feet high to the floor. In less than half a minute it had reached the top, and was struggling hard to get still higher. I took it down, and again placed it at the bottom. Up it went as fast as before; and this was repeated nine times with exactly the same result. For the tenth time I placed the persevering creature at the bottom of the curtain; and, after it had walked about halfway up, it suddenly stopped, apparently quite satisfied with having travelled a distance of over seventy feet in an upward direction. Its six legs were immediately arranged symmetrically in a business-like manner, and there it settled quite still, as if it had some definite object in stopping just exactly in that spot.
But we must now return to our own insect, which has by this time settled itself in a similar manner on the stick we provided for it. The peculiar organs which represent the wings, though so very small, show distinctly, in miniature, the colour and pattern of the fully developed wings of the species. An interesting change is just now commencing. These wings are apparently growing larger, but the development is very unequal, so that they become curled and crumpled till they are even more unsightly than before. All seems to be going amiss. But this lasts only for a short time. The fluid from the body steadily rushes into the nervures, causing the wings to expand, and in a few minutes the beautiful pinions are stretched to the full extent, assume their normal shape, and expose the full glory of their brilliant colours.
It may be interesting if I give an example showing the exact time taken for the full development of the wings of a certain insect. So I will here quote an entry from my note book; and, by the way, let me strongly advise all my young readers who follow up this subject to habitually enter in a book kept specially for the purpose all facts which strike them as they pursue their study of nature. The note to which I refer runs as follows:
'Early on the evening of the 22nd [April] I selected a few chrysalides of Populi [the Poplar Hawk Moth, page 209] which, from the looseness of their cases, were thought to be just on the point of emerging. At 8.46 one of them showed signs of restlessness; and, after a few vigorous movements, during which it rolled itself over on the glass [I had placed the pupæ on a piece of plate glass so that slight movements might be more easily detected], the front of its case was suddenly thrust off with considerable force; and in less than four seconds the imago was quite free and crawling on the table. After trying hard to reach a higher point than was provided for about four minutes, it rested to expand its wings – now about seven-sixteenths of an inch long, or one-third the total length of the body. At 9 o'clock the wings reached half the length of the body, and were much curled. At 9.12 they were fully expanded and straightened out.'
From this extract we see that the whole period from the bursting of the case to the full expansion of the wings was only twenty-six minutes; and it will be well to remind the reader that the process occupies even a much shorter time than this with many species, both of butterflies and moths. It will be observed, also, that the evening was chosen as the time for the observation. There was a reason for this. The Poplar Hawk Moth, as is the case with many others, almost invariably emerges from the chrysalis in the evening – usually after dark. But it may be mentioned in passing that a far larger number of the Lepidoptera as invariably emerge in the morning.
Again we will return to our newly emerged insect, for there are still one or two interesting points to observe. The wings have fully expanded, it is true, but how very limp they are! Take the creature on the tip of your finger and hold it so that its body is in a horizontal position. Immediately the wings bend downward with their own weight, so soft and flexible are they. The body, too, is still very soft, and apparently much too heavy for flight. Then, if you place it on a flat surface, it will immediately try to find some perpendicular or overhanging surface from which it can suspend itself by means of its legs, so that the pendant and straightened wings are in the best