SPATIAL-DISTRIBUTION OF THE EARLY LARVAE AND COCOONS OF THE PINE SAWFLY NEODIPRION-XIANGYUNICUS (XIAO AND HUANG) (HYM, DIPRIONIDAE) IN CHINA, AND DETERMINATION OF AN OPTIMAL-POPULATION SAMPLING PROGRAM

In this paper we report on investigations into the spatial distributio n pattern and optimum field sampling methods for the pine sawfly Neodi prion xiangyunicus, a serious defoliator of Pinus yunnanensis in China . The early instar larvae are mainly distributed on the current year's needles on the lowest shoots at the perimeter of the tree crown, whil e the cocoons are found mainly in the layer of the soil litter closest to the trunk, these being the optimal sampling sites for maximising t he chances of locating sawflies. Using IWAO's Regression Method, both early larvae and cocoons show a between-tree distribution aggregated w ithin colonies, that is, some trees having significantly more sawflies than others. Early larvae also show significant clumping within group s of trees, but cocoons do not. Models expressing the relationship bet ween the proportion of uninfested trees and population density, theore tical sample size and sample accuracy are also presented.