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 {19} 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. But, supposing that it has escaped this great danger, we now see the creature in its completest form, as the IMAGO, OR PERFECT BUTTERFLY. The first term, _Imago_, is a Latin one, merely signifying an image, or distinct unveiled form; as distinguished from the previous _larva_, or masked state, and the _pupa_, or swathed and enveloped state. The word _imago_ then, in works on entomology, always means the {20} perfect and last stage of insect life, and is applied to all insects with wings--for it must be borne in mind that no insect is ever winged till it reaches the last stage of its existence. If the progressive development of these lovely beings is so marvellous, no less so is their structure when perfected, and of this some general description must now be attempted.