Abstract:The pine sawfty, Acantholyda posticalis Mastsumura, is a destructive pest of Pinus sylvestris, P. tabulaeformis and P. koraiensis. It was found that Formica fukaii is an important predato of the sawfly in Heilongjiang Province. The nests are built on the ground, but some nests are built on Carex sp. About 1340 larvae can be predated by the ants in a nest per day. The habits, nesting means, and relocation of the nests are discussed.