Evaluation of Mortality During the Cocoon Stage of the Larch Sawfly, Pristiphora erichsonii (Htg.)

Abstract

This is one of a series of papers on the development of life tables for the larch sawfly, Pristiphora erichsonii (Htg.), by a research team at Winnipeg. Previous papers have described techniques for obtaining population estimates for eggs, cocoons, and adults (Ives, 1955; Ives and Turnock, 1959; Turnock, 1960), and current work is concerned with the development of methods of segregating and evaluating the mortality factors affecting each stage. This paper describes the methods used to evaluate the amount of mortality caused by individual factors in the cocoon stage and discusses the problems of obtaining accurate and unbiased estimates.