“If you please, what is that long piece which seems to be growing from the tip of your body? It looks like Mary’s stove hook when she sticks it in the lid.” “That,” was the rather short answer, “is my abdomen, and it isn’t growing from the tip of my body, but from the _top_ of my thorax. It seems to me you have never seen an ensign fly before.” “No, I never did. Please, what does ensign mean?” “The dictionary will tell you that. All I know is some man got an idea that we carried our abdomens aloft like a flag or ensign, and so named us ensign fly. We are not flies, to begin with, but we have to keep any idiotic name they choose to tack on us. Now take Mrs. Horntail, who wants——” “Thank you, I can speak for myself,” interrupted the horntail, sharply. She was quite handsome, with her black abdomen banded with yellow, her red and black head, yellow legs and horn, and dusky wings. “I like my name. It means something, for I have a horn on my tail, and, what’s more, I use it. You should see me bore into solid green wood. None of your dead wood for me. I am not content with one hole either. I bore a great many, and in each I drop an egg, and when my babies hatch they get fat on the sap wood of the tree.” “There seem to be such a lot of things to eat trees,” said Ruth. “Perhaps there are, but I am interested in horntail babies only. They do their share of eating too, and when they grow sleepy they make cocoons of chips and silk from their own bodies, and go to sleep. After they wake they are changed into winged creatures, who naturally do not care to live in the tree any more. So they gnaw their way through the bark to the outside world and——” “Not if the woodpeckers and I can help it,” interrupted an ichneumon fly, keeping her antennæ in constant motion. She seemed to have long streamers floating from the back of her, and, altogether, Ruth thought her even queerer looking than the ensign fly. “Those streamers are my ovipositor,” she explained to Ruth. “The thing I lay eggs with, you understand. When I shut them together they form a sort of auger, with which I bore into a tree, way, way in, where the fat horntail babies are chewing the sap wood, and so ruining the tree. Into their soft bodies I lay my eggs and when my children hatch they eat, not the tree, but the horntail baby. It is a wonderfully good riddance, and so the farmer and fruit grower consider us their friends and call us ‘trackers,’ because we find the hiding places of so many pests that harm the plants.” “You can’t get my babies,” said Mrs. Saw Fly. “I haven’t a horn, but I have a saw, and, though it will not bore into wood, it saws fine gashes in green leaves. Of course I drop an egg in each gash, and soon there’s a swelling all around it, and when my children hatch they rock in gall nut cradles, and the sap which gathers there is their food.”