The hairy ground beetle (Chlaenius quadrisulcatus (Paykull)) (Coleoptera: Carabidae) in central Sweden - activity, mandible wear and age

A population of the rare carabid, Chlaenius quadrisulcatus (Paykull), was discovered on a protected bog in central Sweden. The beetles were collected using pitfall traps, connected with a gutter, and embedded into large Sphagnum-hummocks. A study of mandible wear patterns and reproductive condition was used to determine the relative age of beetles. Their gut contents were also identified to analyze whether the intake of hard food could be one of the factors contributing to increased mandible wear. A comparison was made with two other adult-overwintering carabid species: Chlaenius costulatus (Motschulsky) and Agonum ericeti (Panzer), both characteristic species in bog habitats. C. quadrisulcatus exhibited a peak of activity in early summer (June), and the majority of collected beetles were found to be in their, at least, second breeding season. Several overlapping breeding cohorts of C. quadrisulcatus might therefore occur throughout the year, but the present investigation was unable to detect neither larvae, nor newly emerged or young individuals of this species. C. quadrisulcatus showed a much higher proportion of individuals with severely worn mandibles than the other investigated species. However, the intake of hard food was found to be higher in A. ericeti than in C. quadrisulcatus. Severe mandible wear in C. quadrisulcatus could, therefore, be caused by intensive biting and burrowing into Sphagnum-hummocks. Moreover, larvae and newly emerged beetles of C. costulatus and A. ericeti were captured in pitfall traps indicating a more pronounced surface activity, among all developmental stages, in these two carabid species. Further investigations are needed to fully examine whether or not the occurrence of large Sphagnum-hummocks are essential for the survival of C. quadrisulcatus.