Eine Beobachtung zur Grundfrage der Abhängigkeit von Wirkungsgrad und Wert natürlicher Feinde gegenüber Schädlingen.

Abstract

Studies covering twelve years were made in high mountains at conifers broken by avalanches, snow or storms. It was their original purpose to determine the Diptera species occurring in these places, but they also served to discover the causes which explained the absence of a possible mass increase of the relatively dense bark-beetle population and its consequences. The decisive factor in this control was the destruction of all stages of the injurious insects by the larvae of four Diptera species. Their mode of life, their efficacy and their value as natural enemies of the bark-beetle show peculiarities in the dependence of the predator on the injurious insect which differ from the normal complex of relations. This is discussed in detail.