The gentles, whilst growing and feeding, are called "green" gentles; their skin is transparent, and in this state chickens do not like eating them; and it is as well so, for then the half-grown gentles would be capable of temporarily becoming deleterious internal parasites in the birds' crop. As soon as they are full grown they crawl away from the food material and will fall through the strainer-like obstruction in the bottom hole of the pot into the pan on the ground underneath. They are then termed clean or "scoured" gentles and are fit for bird-food or for fishing-bait. If taken out of the pan and placed in boxes with a little sand, they will keep three days, more or less, according to the weather; they then pupate, and in a few days, or weeks, or months, according to temperature, emerge as blue-bottles. As pupæ they are good and convenient food for domestic fowls, and for all pheasants and like game-birds. If receptacles as above directed are situate in a fowl-run, the hens will never leave the ground dish unwatched as long as full fed gentles are maturing. Hens thus fed are prolific layers of eggs, but of course they must be otherwise fairly fed with farinaceous and suitable other food and healthy grit. The maggots of no other flies are worth similarly cultivating; those that feed on vegetable refuse are more offensive in smell than common gentles; the maggots of the fungus flies are comparatively clean creatures and free from bad smell, but the largest are small. CHAPTER XIII A CAMPAIGN OF EFFECTIVE WARFARE Several authors of recent books, and lately also able lecturers, have done much to awaken people to a realisation of the dangers of our ever recurrent summer plague of flies. The advent of the petrol motor-car and other automobile vehicles has at the most but very slightly improved the state of affairs within town areas, where mews were formerly much more numerous. The public press has followed suit, but something more in the way of a sustained effort for hygienic reform is desirable. The terrible European war should not preclude consideration of the subject, for the scourges of fly-borne contagion have ever followed armies and rivalled the casualties of the very battlefield. Bands of enthusiasts everywhere should keep going a veritable anti-fly campaign as one of the most urgent needs of practical sanitation. Otherwise active support of the cause will soon languish and be obliterated amongst the multitudinous ever-changing questions of the day, political and other, which, as newspaper editors are persuaded, have the attention of the public for the time being. In spite of the incontestible prospects of universal benefit it may not be easy to engage a large body of public support without something like an organised propagandist movement.