This index is devoted to pests or presumed pests, although a few are mentioned briefly in other indexes. Some are included here only because they evoke fear or curiosity. Though harmless, they are responsible for more calls to entomologists and pest control operators than is justified by their impact as pests or nuisances. Others can be serious pests, usually under certain conditions that result in a rapid increase of a species to epidemic proportions. Residential or other buildings may be entered merely because they are in the path of a mass migration of some species. In other cases, the pests are seeking a protected harborage.