When the moth first sees the day, it is humid and moist; but this humidity soon evaporates, the interior parts dry and harden as well as the exterior; the wings, which are wrinkled, being thick and small, then extend themselves, strengthen and harden insensibly, and the fibres which were at first flexible, become hard and stiff; so much so, that Malpighi considered them as bones: in proportion as these fibres harden, the fluid which circulates within them, and extends the wings, loses its force; so that if any extraneous circumstance prevent the motion of this fluid, at the first instant of the moth’s escape from its former state, the wings will then become ill-shaped; often expanding with such rapidity, that the naked eye cannot trace their unfolding. The wings, which were scarce half the length of the body, acquire in a few minutes their full size, so as to be nearly five times as large as they were before: nor is it the wings only which are thus increased; all their spots and colours, heretofore so minute as to be scarce discernible, are proportionably extended, so that what before appeared as only so many unmeaning and confused points, become distinct and beautiful ornaments; and those that are furnished with a tongue or trunk, curl and coil it up. When the wings are unfolded, the tongue rolled up, the moth sufficiently dried, and the different members strengthened, it takes its flight. Most of them, soon after they have attained their perfect state, void an excrementitious substance; Reaumur thinks that they eject very little, if any, during the rest of their lives.
In the progress of these insects, such changes take place, as we could have formed no conception of, if the great Author of these wonders had not been pleased to reward the industrious naturalist with the discovery.
If the moth be opened down the belly, and the unctuous parts which fill it, be removed, the gross artery, which has been called the heart, will be visible, and the contractions and dilatations, by which it pushes forward the liquor it contains, may be easily observed. One of the most remarkable circumstances is, that the circulation of this fluid in the moth is directly contrary to that which took place in the caterpillar; in this, the liquor moved from the tail to the head, whereas in the moth, it moves from the head to the tail; so that the fluid which answers the purposes of the blood in the moth, goes from the superior, towards the inferior parts, but in the voracious sensual caterpillar, the order is inverted, it proceeds from the inferior towards the superior parts; all its members, formerly soft, inactive, and folded up under an envelope, are expanded, strengthened, and exposed to observation.