To purge the earth of death's impurities and cause deceased animal matter to be once more numbered among the treasures of life there are hosts of sausage queens, including, in our part of the world, the bluebottle (Calliphora vomitaria, LIN.) and the checkered flesh fly (Sarcophaga carnaria, LIN.). Every one knows the first, the big, dark-blue fly who, after effecting her designs in the ill-watched meat safe, settles on our window panes and keeps up a solemn buzzing, anxious to be off in the sun and ripen a fresh emission of germs. How does she lay her eggs, the origin of the loathsome maggot that battens poisonously on our provisions, whether of game or butcher's meat? What are her stratagems and how can we foil them? This is what I propose to investigate. The bluebottle frequents our homes during autumn and a part of winter, until the cold becomes severe; but her appearance in the fields dates back much earlier. On the first fine day in February, we shall see her warming herself, chillily, against the sunny walls. In April, I notice her in considerable numbers on the laurestinus. It is here that she seems to pair, while sipping the sugary exudations of the small white flowers. The whole of the summer season is spent out of doors, in brief flights from one refreshment bar to the next. When autumn comes, with its game, she makes her way into our houses and remains until the hard frosts. This suits my stay-at-home habits and especially my legs, which are bending under the weight of years. I need not run after the subjects of my present study; they call on me. Besides, I have vigilant assistants. The household knows of my plans. Every one brings me, in a little screw of paper, the noisy visitor just captured against the panes. Thus do I fill my vivarium, which consists of a large, bell-shaped cage of wire gauze, standing in an earthenware pan full of sand. A mug containing honey is the dining room of the establishment. Here the captives come to recruit themselves in their hours of leisure. To occupy their maternal cares, I employ small birds--chaffinches, linnets, sparrows--brought down, in the enclosure, by my son's gun. I have just served up a Linnet shot two days ago. I next place in the cage a bluebottle, one only, to avoid confusion. Her fat belly proclaims the advent of a laying time. An hour later, when the excitement of being put in prison is allayed, my captive is in labor. With eager, jerky steps, she explores the morsel of game, goes from the head to the tail, returns from the tail to the head, repeats the action several times and at last settles near an eye, a dimmed eye sunk into its socket.