When Spallanzani, [51] after blinding some Bats, released them in a room converted into a maze by means of cords stretched in every direction and of heaped-up brambles, how were those animals able to find their way about, to fly quickly, to move to and fro, from end to end of the room, without hitting the interposed articles? What sense analogous to any of ours guided them? Would some one tell me and, above all, make me understand? I should also like to understand how the Ammophila infallibly finds her caterpillar’s burrow with the aid of her antennæ. It is not a case of the sense of smell: we should have to presume it to possess an unparalleled delicacy, while recognizing that it is exercised by an organ in which no provision seems made for the perception of smells. What a number of other incomprehensible things do we not ascribe to the insect’s sense of smell! We are satisfied with a word: the explanation is ready-found, without laborious search. But, if we care to consider the matter thoroughly, if we compare the requisite array of facts, then the cliff of the unknown rises abruptly, not to be climbed by the path which we insist on following. Let us then change our path and admit that animals may have other means of information than our own. Our senses do not represent the sum total of the methods whereby an animal communicates with that which is not itself: there are others not capable of comparison, however remote, with those which we possess. If the act of the Ammophila were an isolated fact, I should not have lingered over it as I have done; but I propose to speak of others stranger still, which will carry conviction to the most exacting mind. After relating them, therefore, I shall return to the subject of special senses, irreducible senses, unknown to us. For the moment, let us go back to the Grey Worm, which it would be as well for us to know in a less casual fashion. I have four of them, dug up with the knife at the spots indicated by the Ammophila. My intention was to substitute them, by turns, for the doomed victim, so as to see the Wasp’s operation repeated. When my plan failed, I placed the worms in a glass jar, with a layer of earth and a lettuce-stalk above them. By day, my captives remained buried in the earth; at night, they came up to the surface, where I caught them gnawing at the salad from below. In August, they dug deep down, not to come up again, and fashioned themselves a cocoon apiece of earth, very rough on the outer surface, oval in shape and the size of a small pigeon’s egg. The moth appeared at the end of the same month. I recognized the Dart or Turnip Moth (Noctua segetum, Hübn.).