The gluttonous Caterpillars do nothing at all but eat, unless we except a curious motion they sometimes indulge in. When several Caterpillars are grazing side by side, you sometimes see all the heads in the row briskly lifted and as briskly lowered, time after time, all together and as accurately as if they were Prussian soldiers drilling. I do not know whether this is their way of showing that they would fight, if necessary, or a sign of pleasure in the eating and the warm sun. Anyhow, it is the only exercise they take until they are full-grown and fat.
After a whole month of grazing, the Caterpillars at last have enough. They begin to climb in every direction. They walk about anyhow, with the front part of their bodies raised and searching space. It is now the beginning of cold weather, and my Caterpillar guests are in a small greenhouse. I leave the door of the house open. Soon the whole crowd have disappeared.
I find them scattered all over the neighboring walls, some thirty yards off. They are under ledges and eaves, which will serve them as shelters through the winter. The Cabbage-caterpillar is hardy and does not mind the cold.
In these shelters they weave themselves hammock cocoons and turn into chrysales, from which next spring the Moths will come.
We may be interested in the story of the Cabbage-caterpillar, but we know that there would be not enough cabbages for us if he were allowed full sway. So we are not ill-pleased to hear that there is still another insect who preys upon him and keeps him from being too numerous. If the Cabbage-caterpillar is our enemy, this insect is our friend. Yet she is so small, she works so discreetly, that the gardener does not know her, has not even heard of her. If he were to see her by accident, flitting around the plant which she protects, he would take no notice of her, would not dream of the help she is giving him. I am going to give the tiny midget her deserts.
Scientists call her by a name as long as she is tiny. Part of the name is Microgaster. It is what I shall have to call her, for she has no other that I know of. You must blame the wise scientists who named her that, and not me.
How does she work? Well, we shall see. In the spring, let us look about our kitchen-gardens. We can hardly help noticing against the walls or on the withered grasses at the foot of the hedges some very small yellow cocoons, heaped into masses the size of a hazel-nut. Beside each group lies a Cabbage-caterpillar, sometimes dead and always looking very tattered. These cocoons are the work of the Microgaster’s family, hatched or on the point of hatching; they have been feeding on the poor Caterpillar.
The little Microgaster or Midge is about the size of a Gnat. When the Caterpillar-moth lays her orange eggs on the cabbage leaves, the Midge hastens up and with a slender, horny prickle she possesses, lays her egg inside the film of the Moth’s egg. Often many Midges lay their little eggs in the same Moth’s egg. Judging by the cocoons, there are sometimes as many as sixty-five Midges to one Caterpillar.