Search for quality parameters to estimate the condition of Pterostichus cupreus (Col., Carabidae) in view of population dynamic modelling

Abstract

Abstract: Habitat quality affects the condition of predatory beetles in terms of size and weight. Carabid body weight and size are defined and measured in many ways. The way of collecting and preserving of beetles affects these parameters. This makes comparison between studies difficult. This paper presents more precise methods to determine the condition of the carabid P. cupreus in farmland. Beetles were caught alive by using pitfall traps and were weighted. Elytra maximum length and area were measured by image analysis. The elytra area appeared to be a good indicator for beetle size. The relative fresh weight was defined as the fresh weight/elytra area. To convert weight from formalin trapped beetles into fresh or dry weight, relationships between different weighing procedures were established. Analyses were made of the relation between various weight and size parameters. The relative fresh weight of both sexes increases significantly early in the season. Weight and relative fresh weight do not differ significantly between sexes. Since females are expected to respond more clearly to environmental circumstances in terms of weight, variability should be higher. This is best reflected in the relative fresh weight which is much more variable in females than in males. Therefore this parameter is most suitable for assessing individual conditions. For P. cupreus the multiplication factor to transform alcohol weight into fresh weight is 1.19. Because all dry, fresh and alcohol weights are highly correlated it depends on the research questions and circumstances which method to choose.