“But, my boy, you don’t suppose the caterpillar is so simple as to make windows here and there in its dwelling and so make it easy for its foes, of which it has many besides man, to attack it! If it should take a fancy, let us say, to go out and get a little fresh air some fine day, a sparrow might spy it and carry it off as a choice titbit for its brood under the roof tiles. All these dangers it knows; or, rather, it guesses them vaguely, for every creature, even to the smallest worm, knows how to protect itself and preserve its species. Unquestionably it lacks the reasoning faculty, which belongs only to man; but it none the less acts as if it reasoned out its own interests with an accuracy that astounds the thoughtful observer. As a matter of fact, my dear children, Another has already reasoned for it, and that Other is the universal Reason in and by whom all live; it is God, the Father of men, and also the Father of lilacs and of the caterpillars that gnaw them. The creature knows, then, without ever having learned; it is master of its art without having been taught; and at the very first trial, with no experience to rely on, it does admirably the thing it was intended to do. This gift bestowed at birth, this unfailing inspiration that guides it in its work, is called instinct. “In its butterfly state the leopard-moth takes very little food, at the most a few drops of honey from the opening flowers. Its proboscis, so slender and so delicate, is fitted to get this food. Now that it no longer has its strong mandibles, how can the moth imagine that wood is eatable? Is it possible that it remembers what it liked as a caterpillar? Who can say? Moreover, how can the moth tell what trees have wood suitable for the larvæ, when we ourselves must have a certain degree of education in order to know the commonest varieties? The moth, with no previous education, never mistakes a plane-tree for a pear-tree, a box-tree for a lilac, an oak for an elm. Thus the eggs are always laid on the right sort of tree, never on any other. Where man might make a mistake, the insect never errs.