The task of locating and reporting insect infestations falls upon the Forest Ranger and other field men of the Forest Service. Since the Rangers are practically the only class of Forest officers that visit all parts of a National Forest during each field season, the Supervisor relies mostly on them to report upon insect infestations. In riding to and from his work, while on fire patrol, while going for mail and supplies, while attending to the timber, grazing and other business of his district, the Ranger does a good deal of traveling and covers practically every part of his district. These are good opportunities to watch for fresh outbreaks of insects, and the wide-awake, progressive Ranger never misses such chances. If he sees reddish-brown masses of pitch and sawdust on the bark of a tree he immediately recognizes it as the work of insects. Or perhaps he may see a pine or a spruce tree with all its needles turned yellow. He knows then that this tree was girdled by bark beetles very recently, probably during the previous summer. A tree whose needles had turned red would indicate to him that the infestation was more than a year old, since trees attacked in the spring of one year usually do not show the results until the following summer. These two stages are known by the trained entomologist as the "yellow-top" and the "red-top" stages respectively. The latter is followed by the "black-top" stage. In this stage, insect infested trees stand out very conspicuously as leafless, gray or black snags, and they tell the story of the work of bark beetles that happened years ago. [Illustration: Figure 47. The first evidence of insect attack are the reddish brown pitch tubes on the bark. Lodgepole pine infested by the mountain pine beetle. Lassen National Forest, California. Photo by the author.] [Illustration: Figure 48. The last stage of an insect-attacked tree. The tree is dead and the dry bark is falling off. Lassen National Forest, California. Photo by the author.]