The antennæ have often been suggested as the seat of a special sense able to guide insects. I have already shown how the amputation of those organs seems in no way to impede the Wasp’s investigations. Let us try once more, under more complicated conditions. I seize the Bembex, cut off her antennæ at the roots, and at once release her. Goaded by pain, maddened at having been imprisoned in my fingers, the insect darts off faster than an arrow. I have to wait for a good hour, very uncertain as to whether it will come back. The Wasp arrives however and, with her unvarying precision, alights quite close to her door, whose appearance I have changed for the fourth time. The site of the nest is now covered with a spreading mosaic of pebbles the size of a walnut. My work, which, as regards the Bembex, surpasses what the megalithic monuments of Brittany or the rows of menhirs at Carnac are to us, is powerless to deceive the mutilated insect. Though deprived of her antennæ, the Wasp finds her entrance in the middle of my mosaic as easily as the same insect, supplied with those organs, would have done under other conditions. This time I let the faithful mother go indoors in peace. Four successive alterations in the site; changes in the colour, the smell, the materials of the outside of the home; lastly, the pain of a double wound: all had failed to baffle the Wasp or even to make her waver as to the precise locality of her door. I had come to the end of my stratagems and understood less than ever how the insect, if it possess no special guide in some faculty unknown to us, can find its way when sight and scent are baffled by the artifices which I have mentioned. A few days later, a lucky experiment reopened the question and allowed me to study it under another aspect. In this case we uncover the Bembex’ burrow all the way along, without changing its appearance too much, an operation made easier by the shallowness of the burrow, its almost horizontal direction, and the lack of consistency of the soil in which it is dug. With this object we scrape the sand away gradually with a knife. Thus deprived of its roof from end to end, the underground dwelling becomes an open trench, a conduit, straight or curved, some eight inches long, open at the spot where the entrance-door used to be and finishing in a blind alley at the other end, where the larva lies amid its victuals.