ANALYSIS OF THE TEMPERATURE-DEPENDENT DEVELOPMENT OF THE SPRUCE BARK BEETLE IPS-TYPOGRAPHUS (L) (COL, SCOLYTIDAE)

Following individual development by means of the 'sandwich method' the duration of egg, larval, and pupal stages, as well as of adult matura tion feeding of the spruce bark beetle (Ips typographus) was measured at constant temperatures in the range between 12 degrees and 33 degree s C. At 20 degrees C complete development from egg to adult emerging f rom pupa averaged 29 days. The proportion of the duration of larval de velopment relative to total preimaginal development increased with tem perature. Developmental rates, i.e. the speed of development increased linearly with temperature in a range between 15 degrees and 25 degree s C. Based on linear regressions, lower developmental thresholds were calculated to be 10.6 degrees C (eggs), 8.2 degrees C (larvae), 9.9 de grees C (pupae), and 8.3 degrees C (preimaginal development egg to pup a), respectively. Differing heat sums reported in the literature match ed ours when recalculated with our developmental thresholds. A nonline ar model (Logan/Lactin) was fitted to the data which allowed to descri be development in the entire temperature range. It further permits to identify lower and upper(approximate to 40 degrees C) developmental th resholds as well as optimum temperatures (30-33 degrees C) of the inst ars.