TEMPERATURE-RELATED DEVELOPMENT OF SPRUCE BARK BEETLES IN MONTANE FOREST FORMATIONS (COLEOPTERA, SCOLYTIDAE)

Two slope profiles covering altidudes from 620 - 1.420 mNN and exposed to N and S, respectively, were investigated during 2 seasons for thei r thermal conditions regarding the development of spruce bark beetle p opulations. Temperature of air and cambium in different positions on t rap trees were recorded continously, in order to calculate the thermal sums available for the broods under different site and weather condit ions. Moreover, flight activity and brood development was observed. In the laboratory the developmental zero and the required thermal sum of Ips typographus (Linnaeus 1758), Ips amitinus (Eichhoff 1871) and Pit yogenes chalcographus (Linnaeus 1761) were experimentally determined. Significant differences between the 3 species were found. Since the da ta from laboratory proved to be valid also in the field, they can be u sed for calculating the developmental potential of these Scolytidae sp ecies under different thermal conditions. The latter differed consider ably due to altitude, exposition, shadowing and weather, thus providin g a wide range of different thermal sums available to the broods. Taki ng into account that Ips typographus cannot hibernate in a subadult st age, the effective period of reproduction during season varies between a few weeks in spring and a few months in summer. The implications fo r population dynamics of Ips typographus and Pityogenes chalcographus are briefly discussed, considering a diapause of adults with Ips typog raphus and the differences between specific modes of hibernation.