The next great loss to the forests is from insects. When insects have bored into wood it becomes honey-combed by the canals cut by the little insects and is utterly valueless. The loss to fruit and forest trees will be taken up more fully in the chapter on insects. At present it is only necessary, in order to show how much our forests suffer in this way, to state that the yearly loss from this cause is placed at no less than $100,000,000 a year, and the loss to fruits is counted at one-fifth of the entire crop. Some slight idea of the danger to our forests will be seen by the simple statement that forty-one different species of insects infest the locust tree, eighty the elm, one hundred and five the birch, one hundred and sixty-five the pine, one hundred and seventy the hickory, one hundred and eighty-six the willow, while oak trees are attacked by over five hundred! This is exceedingly difficult to control and can perhaps never be entirely checked. Some remedies will be suggested later, and by having smaller forests, more carefully watched, some personal care can be given to the trees. In Germany the trees are as closely watched as are other crops, and the saving in value well repays this extra care and expense. A much smaller loss comes from the winds that sometimes level all the trees over many square miles. This can not, of course, be prevented, except possibly in the turpentine forests, but care should be taken to use all the wood, never allowing it to decay where it fell, and also to replant the land with trees, unless it is fitted for agriculture. A great saving of the forests may be effected by what is called preservative treatment, which consists of treating railroad ties, piling, mine timbers, poles, and posts with creosote or zinc chlorid to prevent decay from the moisture of the ground or from injury by salt-water borers. The use of creosote is almost double the cost of zinc chlorid, but it is much more effective and durable. A fence post can be treated with creosote for about ten cents, a railroad tie for twenty cents, and a telephone pole for from seventy-five cents to a dollar. In every case the timber treated will last twice as long as it would without such treatment and in view of the present high prices it is bad business policy to use timber in such a way that it will need replacing soon. It is estimated that if all timbers which could be profitably treated were so cared for, it would mean a money saving to the owners of $47,000,000, and an annual saving in wood equal to 4,000,000,000 board feet of lumber. The next point in the conservation of the forests is to seek substitutes to take the place of wood. There are many uses of wood which nothing else will satisfactorily supply. For example, no railroad cross-tie has ever been designed of other material that does not increase the danger of railway accidents, though over two hundred kinds have been patented.