One would think that with such an array of enemies, the forest would hardly survive, but on the other hand there are many enemies of these pests. The most destructive are the predaceous and parasitic insects. Many insects are simply predaceous, pouncing upon and destroying such other insects as they can overcome. Still others are parasites, some external, but most of them living within the bodies of their victims where they pass their entire larval life. The eggs are laid on or in the body of the victim, so that as soon as one hatches, it has suitable food. The ichneumon fly, Fig. 103, is such a parasite; it destroys millions of insect pests. It has a long and peculiar ovipositor with which it drills a hole into the tree and deposits the egg in a burrow of the Pigeon Horntail, a wood wasp that burrows into deciduous trees. The larva soon finds its victim, the grub of the Pigeon Horntail, and lives on it to its destruction. [Illustration: Fig. 103. Ichneumon Fly whose Larva Feeds on the Larva of the Pigeon Horn-tail.] It would seem that it is a hopeless task to control the insect enemies of forest trees and forest products or to prevent losses from their ravages, but the writer is informed by Dr. A. D. Hopkins, the expert in the Bureau of Entomology in charge of forest insect investigations, that the results of their investigations show conclusively that there are many practical and inexpensive methods of control now available thru the suggestions and recommendations in recent Department publications on forest insects, as well as thru direct correspondence with the Department. These methods are based on the principle of prevention and not on that of extermination. It has been shown that thru proper adjustment of the details in management of forests and of the business of manufacturing, storing, transporting, and utilizing the products a large percentage of the losses can be prevented at small additional expense, and that even when considerable cost is involved the amount saved will often represent a handsome profit. THE NATURAL ENEMIES OF THE FOREST. REFERENCES:[A] (1) Meterological. Pinchot, _Primer_ I, pp. 75-76. Roth, _First Book_, _pp._ 198-202. Bruncken, pp. 27-29. Water. Roth, _First Book_, p. 27. Snow, ice and frost. Pinchot, _Primer_, I, p. 76. Bruce, _For. and Irr._, 8: 159, Ap. '02. (2) Vegetable. Roth, _First Book_, p. 4. Boulger, pp. 70-75. Spaulding, _For. Bull._, No. 22. Ward, Chaps. V, VI, VII. Sickles, pp. 41-45. von Schrenck, _For. Bull._, No. 41, Pl. III. Sherfesee. _For. Circ._ No. 139. von Schrenck, _Bur. Plant Ind. Bull._ No. 36. von Schrenck, _Bur. Plant Ind. Bull._ No. 32. von Schrenck, _Agric. Yr. Bk._, 1900, p. 199. (3) Animal.