Abstract:Distribution patterns of the pine sawfly (Neodiprion xiangyunicus) were investigated in relation to site elevation and forest stand density. The pine sawfly was found to be restricted to pure stand of its host at specific elevations based on transect studies. Defoliation and oviposition on Yunnan pine(Pinus yunnanensis) by N.xiangyunicus was confined to a specific elevational band (1900~2100m) within the host range of the area(1650~2100m). Stand density did not appear to have a significant influence on N.xiangyunicus distribution pattern. The defoliation and oviposition by N.xiangyunicus were divided into different levels based on the site elevation. The toughness, length and width of pine needle in 1700m and 1950m sites, the needle dry weight, total nitrogen, tissues of needle, terpenes of needle oils in 1700m,1950m and 2050m sites were researched. It was found that the toughness of needle in 1700m and 1900m sites, the thickness of epidermis, the diameter of resin ducts, the total nitrogen and the dry weight of needle in 1700m, 1950m and 2050m sites had a close relation to the defoliation and oviposition by N.xiangyunicus. The pine sawfly was distributed in the site with higher elavation lower needle toughness, smaller thickness of epidermis, lower nitrogen content and lower dry weight of needle.