ABUNDANCE AND EMERGENCE OF SPRUCE CONE INSECTS IN DIFFERENT PARTS OF SWITZERLAND

In 1989 a total of 4471 spruce cones was harvested at 29 locations dis tributed over the five main geographic regions of Switzerland, i.e. Ju ra, Central Plateau, North, Central and South Alps. The cones were inc ubated in a controlled environment chamber and the emerging insects we re collected and identified. This analysis excludes parasitoids except for the most abundant Torymus spp. Twelve insect species and some 140 00 individuals in total were identified. On the average, every cone wa s inhabited by three insects. The most numerous species were Kaltenbac hiola strobi (Winn.), Cydia strobilella (L.), and Torymus spp., amount ing together to 95% of the total insect number. Though the abundance p eaks varied for different species, most insects were reared from cones from the alpine area. Vegetation type (alliance) was related to the a bundance of several species but did not correlate with total infestati on rate. For two species their number was related to sampling site alt itude. Likewise, a positive, linear correlation was found between the frequencies of the parasitoid Torymus spp. and its host K. strobi, the ratio between the two species averaging 0.7. Cone setting did not cor relate with infestation level, but tree age was positively related to total insect number per cone. In the laboratory C. strobilella and K. strobi were the earliest species to emerge; they had the shortest emer gence period as well. The percentage of K. strobi with prolonged diapa use (emergence in second year after cone sampling) was 51%, while the corresponding values for all other species were lower than 20%. Neithe r sampling site elevation nor cone setting affected diapause length.