Life-Table Construction and Analysis in the Evaluation of Natural Enemies

Abstract

Studies evaluating the impact of natural enemies on their hosts fall into two broad categories. The first category involves separate host populations: one population with a particular natural enemy; the other without it. When the resulting densities and mortalities in the populations are compared, the differ­ ences are attributed to the natural enemy. Evaluations of this type quantify the impact of the natural enemy largely in terms of the amount of mortality that is caused by an agent to a given generation or set of generations of the host and the consequent overall reduction in host density; however, these evaluations do not provide descriptions of other sources of mortality that act together with the natural enemy. This approach was reviewed recently (83). The second category involves the construction and analysis of life tables for affected populations, and this is done either for single or multiple locations or generations. This particular use of life tables may be directed at two distinct types of questions regarding the action of natural enemies: (a) They may be