The antennæ have been often suggested as the seat of a special sense to guide insects. I have already shown how the suppression of these organs appears to offer no obstacle to the researches of the Hymenoptera. Let us try once more in wider conditions. The Bembex is caught, its antennæ amputated to the roots, and is then released. Stung by the pain—wild with terror at being held between my fingers—the insect flies off swifter than an arrow. I had to wait a whole hour, uncertain as to its return. However, it came, and with its invariable precision alighted quite close to its doorway, whose look I had changed for the fourth time, having covered the site with a large mosaic of pebbles the size of a nut. My work, which, compared to the Bembex, surpassed what for us are the Megalithic monuments of Brittany, or the lines of Menhirs at Carnac, was powerless to deceive the mutilated insect. Though deprived of antennæ it found the entrance in the midst of my mosaic as easily as would have done an insect under other conditions. This time I let the faithful mother go home in peace. The site transformed four times over, the outworks of the abode changed in colour, scent, and material, the pain of a double wound,—all failed to disconcert the Hymenopteron or even to make her doubtful as to the precise locality of her doorway. I had exhausted my stratagems, and understood less than ever how the insect, if it have no special guide in some faculty unknown to us, can find its way when sight and smell are baffled by the artifices of which I have spoken. Some days later an experience gave me the opportunity to take up the problem from a new point of view. The Bembex burrow had to be bared in its whole extent, without quite destroying it, to which operation its shallowness and almost horizontal direction, and the light soil in which it was made, lent themselves readily. The sand was gradually scraped off with the blade of a knife, and thus, deprived of roof from end to end, the underground abode became a semi-canal or conduit, straight or curved, some eight inches long, open where was the entrance, and ending in a cul-de-sac where lay the larva amid its food. The dwelling was uncovered in full sunshine; how would the mother behave on her return? Let us consider the question scientifically. The observer may be greatly embarrassed: what I have already seen leads me to expect it. The mother’s impulse is to bring food to her larva, but to reach this larva she must first find the door. Grub and entrance are the points which appear to deserve being separately examined; therefore I take away grub and food, and the end of the passage is cleared. There is nothing more to do but arm one’s self with patience.