AN APPRAISAL OF TWO METHODS OF ANALYZING INSECT LIFE TABLES

Abstract

Abstract Two methods of analyses, Morris’ key-factor analysis and Varley and Gradwell’s method of analysis, purport to detect density-dependent and density-independent mortality. To test their claims, both methods were used to analyze a life table constructed from a model in which the mode of action of each mortality factor is known. The results show that Morris’ method can detect variation in mortality between generations but it cannot distinguish the density relationships of that mortality. On the other hand, Varley and Gradwell’s method of analysis was found to detect the density relationships of the mortality as it was modeled, when their modified method, the ’proof of density dependence test,’ is used in conjunction with the linear regression of k-value against the density on which it acts.