It is plain that the mother cannot place her egg in the Bee’s cell, which is closed and barricaded with a cement wall. To pierce it she would have to become a boring-tool once more, and get into the cast-off rags which she left at the doorway of the exit-tunnel. She would have to become a pupa again. For the full-grown Fly has no claws, nor mandibles, nor any implement capable of working its way through the wall. Can it be, then, the grub that makes its own way into the storeroom, that same grub that we have seen sucking the life out of the Bee’s larva? Let us call the creature to mind: a little oily sausage, which stretches and curls up just where it lies, without being able to shift its position. Its body is a smooth cylinder, its mouth a circular lip. It has no means whatever of moving; not even a hair or a wrinkle to enable it to crawl. It can do nothing but digest its food. It is even less able than the mother to make its way into the Mason-bee’s dwelling. And yet its provisions are there: they must be reached: it is a matter of life and death. How does the Fly set about it? In the face of this puzzle I resolved to attempt an almost impossible task and watch the Anthrax from the moment it left the egg. Since these Flies are not really plentiful in my own neighbourhood I made an expedition to Carpentras, the dear little town where I spent my twentieth year. The old college where I made my first attempts as a teacher was unchanged in appearance. It still looked like a penitentiary. In my early days it was considered unwholesome for boys to be gay and active, so our system of education applied the remedy of melancholy and gloom. Our houses of instruction were above all houses of correction. In a yard between four walls, a sort of bear-pit, the boys fought to make room for their games under a spreading plane-tree. All round it were cells like horseboxes, without light or air: those were the class-rooms. I saw, too, the shop where I used to buy tobacco as I came out of the college; and also my former dwelling, now occupied by monks. There, in the embrasure of a window, sheltered from profane hands, between the closed outer shutters and the panes, I kept my chemicals—bought for a few sous saved out of the housekeeping money. My experiments, harmless or dangerous, were made on a corner of the fire, beside the simmering broth. How I should love to see that room again, where I pored over mathematical problems; and my familiar friend the blackboard, which I hired for five francs a year, and could never buy outright for want of the necessary cash! But I must return to my insects. My visit to Carpentras, unfortunately, was made too late in the year to be very profitable. I saw only a few Anthrax Flies hovering round the face of the cliff. Yet I did not despair, because it was plain that these few were not there to take exercise, but to settle their families.