During the periods in which the insects are held in check the woodpecker ranges through the forest, inspecting tree after tree. Many times, during their tireless rounds of search and inspection, I have followed them for hours. On one occasion in the mountains of Colorado I followed a Batchelder woodpecker through a spruce forest all day long. Both of us had a busy day. He inspected eight hundred and twenty-seven trees, most of which were spruce or lodge-pole pine. Although he moved quickly, he was intensely concentrated, was systematic, and apparently did the inspection carefully. The forest was a healthy one and harbored only straggling insects. Now and then he picked up an isolated insect from a limb or took an egg-cluster from a break in the bark on a trunk. Only two pecking operations were required. On another occasion I watched a hairy woodpecker spend more than three days upon one tree-trunk; this he pecked full of holes and from its vitals he dragged more than a gross of devouring grubs. In this case not only was the beetle colony destroyed but the tree survived. Woodpecker holes commonly are shallow, except in dead trees. Most of the burrowing or boring insects which infest living trees work in the outermost sapwood, just beneath the bark, or in the inner bark. Hence the doctor does not need to cut deeply. In most cases his peckings in the wood are so shallow that no scar or record is found. Hence a tree might be operated on by him a dozen times in a season, and still not show a scar when split or sawed into pieces. Most of his peckings simply penetrate the bark, and on living trees this epidermis scales off; thus in a short time all traces of his feast-getting are obliterated. I have, however, in dissecting and studying fallen trees, found a number of deep holes in their trunks which woodpeckers had made years before the trees came to their death. In one instance, as I have related in "The Story of a Thousand-Year Pine" in "Wild Life on the Rockies," a deep oblong hole was pecked in a pine nearly eight hundred years before it died. The hole filled with pitch and was overgrown with bark and wood. [Illustration: WOODPECKER HOLES IN A PINE INJURED BY LIGHTNING]