For several decades after the creation of Yellowstone National Park in 1872, protection of its biological and other resources was haphazard. For example, elk and bison were exploited to near extinction, prompting aggressive protection of them, which included extermination of the native gray wolf from the park. In those years, tourists were not discouraged from handing out tidbits to bears or even gazing into Old Faithful between eruptions (Fig. 1). Such experiences and the advancement of scientific knowledge have resulted in a more passive management policy, wherein disruptive human influences are reduced in favor of an environment in which natural processes are allowed to run their course. Less well known, however, is the turbulent history of forest-inhabiting insects in the park that began in 1922 with the discovery of defoliated Douglasfir trees in the Blacktail Deer Creek drainage. This account describes that occurrence and subsequent outbreaks, particularly of defoliators and bark beetles; the circumstances responsible for what now seem to have been inappropriate, and futile actions to control them; and the lessons learned.