BIOLOGY AND INITIAL DISPERSAL OF OLESICAMPE (HOLOCREMNUS) SP. NR. NEMATORUM (HYMENOPTERA: ICHNEUMONIDAE), A PARASITE OF THE LARCH SAWFLY RECENTLY ESTABLISHED IN MANITOBA

Abstract

AbstractOlesicampe (Holocremnus) sp. nr. nematorum (Tschek) has become established at two locations in Manitoba, and has built up rapidly in both. In 1965 at Pine Falls, where it was released in 1961, 61% of the hosts were parasitized in the vicinity of the release point, and at Riverton, where it was released in 1962–1963, 87% were parasitized. A number of characteristics seem to endow this parasite with a marked ability to act against the larch sawfly. These include good synchronization, longevity and searching capacity; low superparasitism; absence of hyperparasitism, and lack of host resistance by encapsulation. O. sp. nr. nematorum has dispersed at least one mile at Riverton and one-half mile at Pine Falls. The percentage parasitism decreases rapidly from the release points to these limits.