The term Chrysalis is applicable to butterflies only, and, strictly, only to a few of these—Chrysalis[[1]] being derived from the Greek χρυσός (chrysos), gold—in allusion to the splendid gilding of the surface in certain species, such as the Vanessas, Fritillaries, and some others.
In the older works on entomology we frequently meet with the term Aurelia applied to this state, and having the same meaning as chrysalis, but derived from the Latin word Aurum, gold.
Here the reader is again referred to [Plate I]. for a series of the principal forms assumed by the chrysalides of our native butterflies, and as these for the most part represent the next stage of the caterpillars previously figured, an opportunity is afforded of tracing the insect's form through its three great changes; the whole of the butterflies in their perfect state being given in their proper places in the body of the work.
The complicated and curious processes by which various caterpillars assume the chrysalis form, and suspend themselves securely in their proper attitudes, have been most accurately and laboriously chronicled by the French naturalist, Réaumur; but his memoirs on the subject, which have been frequently quoted into the larger entomological works, are too long for insertion here in full, and any considerable abbreviation would fail to convey a clear idea of the process, on account of the intricacy of the operations described. So I can only here allude to the difficult problems that the creature has to solve, referring the reader to the above-mentioned works for a detailed description of the manner of doing so; or, better still, I would recommend the country resident to witness all this with his own eyes. By keeping a number of the caterpillars of our common butterflies, feeding them up, and attentively watching them when full-grown, he will now and then detect one in the transformation act, and have an opportunity of wondering at the curious manœuvres of the animal, as it triumphs over seeming impossibilities.
By reference to the figures of chrysalides on [Plate I]. it will be seen that there are two distinct modes of suspension employed among them; one, by the tail only, the head hanging down freely in the air:—in the other, the tail is attached to the supporting object; but the head, instead of swinging loosely, is kept in an upright position by being looped round the waist with a silken girdle.
To appreciate the difficulty of gaining either of the above positions, we must bear in mind that, before doing so, the caterpillar has to throw off its own skin, carrying with it the whole of its legs, and the jaws
too—leaving itself a mere limbless, and apparently helpless mass—its only prehensile organs being a few minute, almost imperceptible hooks on the end of the tail; and the required position of attachment and security is accomplished by a series of movements so dexterous and sleight-of-hand like, as to cause infinite astonishment to the looker-on, and, as Réaumur justly observes, "It is impossible not to wonder, that an insect, which executes them but once in its life, should execute them so well. We must necessarily conclude that it has been instructed by a Great Master; for He who has rendered it necessary for the insect to undergo this change, has likewise given it all the requisite means for accomplishing it in safety."