Having safely cleared itself free of the chrysalis shell, the butterfly makes its way to some suitable twig, spray, or other object, from which it can hang, sometimes in an inverted position, whilst a very important function takes place. This is the distention and drying of the wings, which at first are very weak and somewhat baggy affairs, although the colour and markings appear upon them in miniature. All other parts of the butterfly seem fully formed, but the helpless condition of the wings alone prevent it as yet from floating off into the air. In a remarkably short time, after the insect has settled to the business, the fluids from the body commence to flow and circulate through the wings, and these are seen gradually expanding and filling out until they attain their proper size. Occasionally there is some obstruction to the equal distribution of the fluids, and when this occurs a greater or lesser amount of distortion, or cockle, in the wing affected is the result. When the inflation is completed the wings are kept straight out for a time; they are then motionless, but all their surfaces are well apart. The wings being now fully developed, the further flow of fluid appears to be arrested. It has been stated by some authorities that this fluid is fibrin held in solution, and that when the work of expansion has been accomplished, the watery medium evaporates, leaving the fibrin to harden, and so fasten together the upper and lower membranes of the wing and to fix the veins, or nerves, in their proper position. Mayer, a specialist on these matters, referring to the expansion of the wings, remarks that the blood [the fluid previously mentioned] forced into the freshly emerged wing would cause it to become a balloon-shaped bag if it were not for fibres that hold the upper and lower walls closely together. The fibres referred to, he states, are derived from those hypodermic cells which do not contribute to the formation of scales, but are stretched out from one wall of the wing to the other. It may be well now to briefly consider some of the structural details of the perfect butterfly, so a beginning will be made with the head (Fig. 6). When looking at the head of a butterfly, the first thing to attract the attention is the very large size of the compound eye (_a_), which seems to take up the largest share of the whole affair. Although so bulky and so complex in the matter of divisions, or facets, as they are termed (the facets are not shown in figure), the power of sight is not really very keen. A butterfly can see things in a general way readily enough, but it seems unable to clearly distinguish one object from another. When engaged in egg-laying, the female butterfly rarely fails to place her eggs on a leaf or spray of the plant that the future caterpillar will feed upon, and it has been suggested that in making this unerring selection the insect is guided more by the sense of smell than by that of sight. [Illustration: FIG. 6.