Estimation of Cocoon Populations of the Larch Sawfly, Pristiphora erichsonii (Hartig)

Abstract

This paper is one in a series on techniques used in estimating populations of various stages of the larch sawfly (Ives, 1955b; Ives and Prentice, 1958). This insect spends most of the year in cocoons in the soil beneath the host tree. The objective of accurate estimation of the cocoon population is to provide a basis for the evaluation of mortality factors affecting this stage. Two methods of estimation are considered in this paper. One is based on soil sampling (Part I) and the other on the number of cocoons formed in traps for falling larvae (Part 11).