A Re-Analysis of the Relationships Between Life Cycle Patterns and the Geographical Distribution of Fennoscandian Carabid Beetles

Abstract

The frequency of the life cycle categories (1) exclusive imaginal hibernators and (2) species which, at least in part, hibernate as larvae, of carabid beetles were studied within fifteen areas in Norway and one area in Finland. These study areas covered most of the climate types found in Norway. The analysis revealed no relationship between the proportion of larval hibernators and the mean air temperatures during the 'critical' months (April, May, September, October) or the coldest month. This contradicts the commonly held view that an Atlantic climate is more favourable for larval hibernators than is a continental climate. However, there was a significant positive correlation between the ratio of imaginal hibernators and the mean air temperatures during the summer. Larval hibernators that are known to have an imaginal diapause during the summer in central or western Europe are absent in the most continental parts of Fennoscandia and this may be because the period favourable for larval development is too short in continental districts. The imaginal hibernators of shady habitats (mostly woodland) generally have a more southern distribution than the imaginal hibernators of the open country. This is attributable to the fact that the season with a relatively warm climate gets shorter as one proceeds from south to north in Scandinavia and that woodland has a cooler micro-climate than habitats of the open country.