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WITHIN AND BETWEEN TREE VARIATION OF LIVE AND PARASITIZED DOUGLAS-FIR TUSSOCK MOTH, ORYGIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE), COCOONS ON WHITE FIR IN CENTRAL CALIFORNIA AND ITS IMPLICATIONS FOR SAMPLING

Published online by Cambridge University Press:  31 May 2012

Robert F. Luck  and
Donald L. Dahlsten
Robert F. Luck
Affiliation:
Department of Entomology, Division of Biological Control, University of California, Riverside 92507
Donald L. Dahlsten
Affiliation:
Department of Entomology, Division of Biological Control, University of California, Riverside 92507
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Abstract

The distribution of Douglas-fir tussock moth, Orgyia pseudotsugata (McD.), cocoons was studied within and between the crowns of white fir, Abies concolor ((Gord. and Glend.) Lindl.), at six locations in the central Sierra Nevada Mountains of California. The within tree, between tree, and between plot distribution of cocoons in the crown, categorized by sex, mortality (including parasitization), and stage (larva or pupa) were analyzed. Only cocoons containing female pupae varied in their distribution within the tree and they were concentrated in the bottom third of the live crown but their densities at any one level bore little relation to those in the other levels within the crown. Cocoon density varied significantly between plots and between trees within plots. Total parasitism did not vary significantly between plots. The variable within tree distribution of cocoons containing female pupae and their increased percentage parasitism relative to those containing male pupae, suggested that the live crown should be stratified. A sample unit consisting of two branches selected from the midpoint of each of the three crown levels (total: 6 branches) sampled approximately 5% of the live crown of white fir. The relation between the number of sample trees and mean cocoon density at three levels of precision is provided.

Type
Articles
Information
The Canadian Entomologist , Volume 112 , Issue 3 , 01 March 1980 , pp. 231 - 238
Copyright
Copyright © Entomological Society of Canada 1980

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