1977 年 12 巻 4 号 p. 313-324
Hunting spiders Oxyopes selatus and O. bodius are common in young pine plantations.The number of 3rd-instar larvae of Lymantria dispar captured by a spider was affected by the hunger of predator and the number of prey, but not exceeded three in 10 days. In a pine plantation, one spider killed less than one 3rd-instar larvae of L. dispar. No aggregation to prey densities was observed. The number of spiders in pine plantations was seemingly determined through dispersal, predation by natural enemies and other factors, and it was not sufficiently large to cause high mortality in macrolepidopterous caterpillars. The role of the spiders in determing the density of the caterpillars was considered as follows. (1)Mortality caused by the predation was negligibly small and inversely density-dependent.(2) Though, when small number of caterpillars was there on a tree, it would be exterminated on the tree. (3) And as the result, the distribution pattern of the caterpillars seemed to become contagious. (4) The spiders, however, could not control the local occurrence of the caterpillars
