Mortality of Larvae of Pterostichus Oblongopunctatus (Fabricius) Col., Carabidae and Philonthus Decorus (Gravenhorst) (Col., Staphylinidae)

Abstract

A description is given of a number of experiments, in the field as well as in the laboratory, in which the mortality of larvae of Pterostichus oblongopunctatus and Philonthus decorus was investigated. Mortality during the larval stage was found to be very high. This applied, at least in Pterostichus, to all three instars. In Philonthus significantly more larvae survived when they were able to find their first meal shortly after hatching. The same tendency was found in Pterostichus. Survival of larvae is strongly influenced by their density and by the availability of food. Probably many larvae do not succeed in finding enough food and die from starvation. Larvae of both species are cannibalistic. Although this cannibalism is reduced when alternative food is available, it does not disappear entirely. Cannibalism occurs even at very low densities (for example in Pterostichus at a density of 15-20 larvae per m 2 ), so it is very likely that under natural conditions (3 _ 8 adults in our study area) cannibalism is an important factor in the regulation of the density of both species.