none Spruce bark infested with Ips typographus was collected from Austria and Switzerland in 1987 and 1988 to provide parasitoid material for investigation. Parasitoid emergence in spring indicated that Coeloides bostrychorum was well synchronised in its flight period with susceptible stages of L. typographus , while Dendrosoter middendorffii emerged earlier than the host beetles. Mating and oviposition are described and an unusual sex ratio for C. bostrychorum is reported. Egg sizes of the three parasitoids are characterised and differences in preferred depth of hosts within the bark are noted. C. bostrychorum with the longest ovipositor can reach all hosts but appears to select only hosts at greater depth than those used by D. middendorffii and Rhopalicus tutela . Oviposition occurs almost exclusively on third instar host larvae. Influences of temperature on adult longevity, juvenile development and diapause are presented indicating that R. tutela may be able to continue development through the winter with no true diapause.