FLY-Tree, in Natural History, a name given by the common people of America to a tree, whose leaves, they say, at a certain time of the year produce flies. On examining these leaves about the middle of summer, the time at which the flies use to be produced, there are found on them a sort of bags of a tough
matter, of about the size of a filbert, and of a dusky greenish colour. On opening one of these bags with a knife, there is usually found a single full-grown fly, of the gnat kind, and a number of small worms, which in a day or two more have wings, and fly away in the form of their parent. The tree is of the mulberry kind, and its leaves are usually very largely stocked with these insect bags; and the generality of them are found to contain the insects in their worm state; when they become winged, they soon make their way out. The bags begin to appear when the leaves are young, and afterwards grow with them; but they never rumple the leaf or injure its shape. They are of the kind of leaf-galls, and partake in all respects, except size, of a species we have frequent on the large maple, or, as it is called, the sycamore.