The following interesting description of the same changes as they take place in the butterfly is from the valuable work of Messrs. Kirby and Spence. "The pupa of a very interesting and beautiful butterfly, the only one of its description that Britain has yet been ascertained to produce, I mean _Papilio Machaon_, being brought to me by a friend early in May, this year, on the sixteenth of that month I had the pleasure of seeing it leave its pupa-case. With great care I placed it upon my arm, where it kept pacing about for the space of more than an hour, when all its parts appearing consolidated and developed, and the animal perfect in beauty, I secured it, though not without great reluctance, for my cabinet, it being the only living specimen of this fine fly I had ever seen. To observe how gradual, and yet how rapid was the development of the parts and organs, and particularly of the wings, and the perfect coming forth of the colours and spots, as the sun gave vigour to it, was a most interesting spectacle. At first it was unable to elevate or even to move its wings; but in proportion as the aërial or other fluid was forced by the motions of its trunk into their nervures, their numerous corrugations and folds gradually yielded to the action, till they had gained their greatest extent, and the film between all the nervures became tense. The ocelli, and spots, and bars, which appeared at first as but germs or rudiments of what they were to be, grew with the growing wing, and shone forth upon its complete expansion in full magnitude and beauty." If we were expert anatomists, and were armed with a good microscope, the study of the wing of a dragon-fly would prove one of great interest to us. These beautiful organs, however, must be examined when they are as yet but a little expanded, as in their completely developed state we should certainly fail in detecting their real structure. Thin and gauze-like as they seem, they are in reality double, consisting of an upper and a lower surface, between which are several parts which are necessary to preserve the shape and carry on the functions of the wings. The two surfaces of the wing enclose what are called the _nervures_, resembling in some respects the veins of a leaf. These are really fine hollow tubes of some firmness, which ramify in large numbers between the two membranes of the wing, and thus give strength and stability of figure to them. Along these tubes, or nervures, branches of the air-vessels, or _tracheæ_, and of the blood-vessels, run.