Egg Production of Pterostichus Oblongopunctatus (Fabricius) (Col., Carabidae) and Philonthus Decorus (Gravenhorst) (Col., Staphylinidae)

Abstract

Egg production of Pterostichus oblongopunctatus and Philonthus decorus has been studied by means of breeding experiments and in preserved material from three different oak forests in the Netherlands. Pterostichus oblongopunctatus produces eggs from April up to the beginning of August, Philonthus decorus from May up to the beginning of September. In 1977 the mean fecundity of Pterostichus oblongopunctatus in breeding boxes in the field was 152 eggs and for Philonthus decorus 45 eggs. Egg production of both species is strongly influenced by temperature. In the case of Pterostichus egg production was also found to be markedly influenced by the availability of food and by population density. There is a significant positive correlation between the actual egg production and the number of mature eggs in the ovaries of Pterostichus oblongopunctatus. On the basis of the data obtained from dissected females the actual egg production is estimated to be 133-254 eggs per female per season during the period of investigation.