It makes no difference that I have seen the Bembex return to her nest hundreds of times; it is always with fresh astonishment that I behold the keen-sighted insect find without hesitation a door whose presence there is nothing to indicate. This door, in fact, is hidden with jealous care, not now, after the Bembex has gone in—for the obliterating sand does not become quite level of its own weight, but leaves perhaps a slight depression, or an incompletely blocked porch—but certainly after she comes out, for, when starting on an expedition, she never fails to put a finishing touch to the result of the natural landslip. Wait for her departure and you shall see her, before flying off, sweep the front of the door and level it with scrupulous care. When she is gone, I defy the most penetrating eye to find the entrance. To discover it again, when the sandy expanse was of any size, I had to resort to a kind of triangulation; and how often, after a few hours’ absence, did not my combinations of triangles and my efforts of memory prove to be at fault! All that remained was the stake, a grass-stalk planted on the threshold; and even this method was not always effective, for the insect, with its passion for continually improving the outside of the nest, often made the bit of straw disappear from sight. CHAPTER XVI A PARASITE OF THE BEMBEX. THE COCOON I have shown the Bembex hovering with her cumbrous prize above the nest and then dropping vertically and very slowly: a hesitating descent accompanied by a sort of plaintive hum. This cautious arrival might suggest that the insect is examining the ground from above in order to find its door and trying to recall the locality before alighting. But another motive is at work, as I propose to demonstrate. Under ordinary conditions, when no sign of danger is apparent, the Wasp comes suddenly, at full tilt, without any hovering, hesitating or whimpering, and settles at once on her threshold or very near it. Her memory is so faithful that she has no need to search about. Let us then look into the cause of that hesitating approach which I described in the last chapter.