An investigation of selected literature indicates that numerous sources of resistance to insect attack have been obtained from plants that evolved in the absence of the insect to which they are resistant. These instances of resistance are not the result of natural selection and this may be beneficially significant in the use of such resistance in agriculture. If agricultural scientists are to capitalize upon such resistance, care must be taken to sequester and preserve the potentially important sources of resistance as well as the important domesticated plants that are currently in jeopardy.