There are various kinds of insects that perform a very useful work in the world, for which they do not always receive credit. When you pass a dead Mole in the fields, and see Ants, Beetles and Flies on it, you shudder and get away from the spot as quickly as possible. You think they are horrid, dirty insects; but they are not; they are busy making the world a cleaner place for you to live in. Let us watch some of these Flies at work, and we shall get an idea of the wonderful things they do in this connection.

You have seen the Greenbottle Flies. They are a beautiful golden-green which shines like metal, and they have red eyes, set in a silver border. They scent dead animals from far away, and rush to lay their eggs in them. A few days afterward, the flesh of the corpse has turned into liquid, in which are thousands of tiny grubs with pointed heads. This is very unpleasant, perhaps you think; but, after all, it is the best and easiest way for dead things to disappear, to be absorbed in the soil and pass on to another form of life. And it is the little Greenbottle worms that produce this liquid.

If the corpse were left undisturbed, it would dry up and take a long while to disappear. The Greenbottle grubs, and the grubs of other Flies as well, have a wonderful power of turning solid things into liquid. When I give the Greenbottle grubs a piece of hard-boiled white of egg to feed upon, they turn it at once into a colorless liquid which looks like water. They have some sort of pepsin which comes out of their mouths and does this work. It is like the gastric juice in our stomach, which dissolves and renders digestible the food we eat. The grubs or worms live on the broth they make in this way until it has all disappeared.

Other Flies whose worms do this work are the Gray Flesh-flies and the big Bluebottles, whom you often see buzzing about the window-panes. Do not let them come near the meat for your dinner, for if they do they will surely make it uneatable. Out in the fields, however, they are in their right element. They give back to life, with all speed, the remains of that which has lived; they change corpses into an essence which enriches our foster-mother earth.