When the fulness of time arrives, the creature breaks through its thin casings, which divide in several places, and the freed insect crawls up into some convenient spot to dry itself, and allow the wings to expand.
All the organs are at first moist and tender, but on exposure to the air soon acquire strength and firmness.
At the moment of emergence, the wings are very miniature affairs, sometimes hardly one-twentieth of their full size when expanded; but so rapid is their increase in volume, that they may actually be seen to grow, as the fluids from the body are pumped into the nervures that support the wing-membrane, and keep it extended.
In the more strongly marked, or richly coloured species, it is a wonderfully beautiful sight to watch this expansion of the wings, and to see the various features
of their painted devices growing under the eye and developing gradually into their true proportions.
Generally within an hour the development is complete, and the wings, having gained their full expanse and consistency by drying in the sun, are ready for flight, and the glad creature wings his way to the fields of air, and enters on that life of sunshine and hilarity which is associated with the very name of "Butterfly."
But not every chrysalis arrives at this happy consummation of its existence. Supposing that you have reared and watched a caterpillar to apparently healthy maturity, that it has duly become a chrysalis, and you are awaiting its appearance in butterfly splendour—peeping into your box some morning to see if the bright expected one is "out," be not surprised if in its stead you find the box tenanted by a swarm of little black flies—an impish-looking crew. Whence came all these? Why they and the empty chrysalis shell are all that remains of your cherished prize; so look no more for the fair sunny butterfly, devoured ere born by that ill-favoured troop of darklings who have just now issued from the lifeless shell.
The truth is, that long since, perhaps in early larva-hood, the creature's fate was sealed; a deadly enemy to his race is ever on the alert, winging about in the shape of a small black fly, in search of an exposed and defenceless caterpillar. Having selected her victim, she pierces his body with a sharp cutting instrument she is armed with, and in the wound deposits an egg; the
caterpillar winces a little at this treatment, but seems to attach little importance to it. Meanwhile his enemy repeats her thrusts till some thirty or forty eggs, germs of the destroyers, are safely lodged in his body, and his doom is certain beyond hope. The eggs quickly hatch into grubs, who begin to gnaw away at the unhappy creature's flesh, thus reducing him gradually, but by a profound instinct keeping clear of all the vital organs, as if knowing full well that the creature must keep on feeding and digesting too, or their own supply would speedily fail; as usurers, while draining a client, keep up his credit with the world as long as they can.
Weaker grows the caterpillar as the gnawing worms within grow stronger and nearer maturity. Sometimes he dies a caterpillar, sometimes he has strength left to take the chrysalis shape, but out of this he never comes a butterfly—the consuming grubs now finish vitals and all, turn to pupæ in his empty skin, and come out soon, black flies like their parent.