THE EFFECT OF HOST TREE ON THE NATURAL ENEMY COMPLEX OF IPS-TYPOGRAPHUS JAPONICUS NIIJIMA (COL, SCOLYTIDAE) IN HOKKAIDO, JAPAN

The effect of host tree on the ecology of the insect natural enemy com plex of Ips typographus was investigated. Tree species was found to in fluence parasitoid composition and abundance, with pteromalids being m ore abundant in Picea jezoensis than in P. abies. Within trees, bark t exture had a significant influence on pteromalid density with higher d ensities occurring in smooth bark. Bark hardness was also shown to aff ect density of both pteromalid and braconid parasitoids. Pteromalid pa rasitoids were found to respond density dependently to host density. P redators showed no consistent response to host tree. Only the clerid p redator Thanasimus substratus showed a density-dependent response to p rey density. A predatory dolichopodid fly, Medetera sp., was shown to be a significant mortality factor for Ips typographus larvae. These re sults are compared to those of previous studies and their relevance to biological control commented upon.