The impact of ground beetle species (Coleoptera: Carabidae) in spruce stands, damaged by Pristiphora abietina (Hymenoptera: Tenthredinidae).

Various species of Carabidae inhabiting spruce stands damaged by Pristiphora abietina (Christ 1791) show significant ecological peculiarities related to their predational meaning. Field studies on the mortality of cocoons of P abietina due to predators show their importance as antagonists. The most important species of ground beetles, antagonistic to P abietina and found in the investigated stands, were ascertained by feeding experiments. Altitude, exposition, age of stands, and vegetation of the sites support or affect the abundance of distinct species of Carabidae, and therefore influence their diversity. Though monocultures of spruce with little ground vegetation impede an optimal diversity of Carabidae, there is no difference of cocoon mortality due to predators between stands with sparse and those with more dense ground vegetation. On impoverished stands, the higher population densities of some of the essential antagonistic species of Carabidae probably compensate the more equally distributed frequencies and the greater diversity of Carabidae on sites with more ground vegetation. Therefore, low diversity of ground beetles does not seem to influence the duration of mass outbreaks of P abietina.