Notes on the Biology and Rearing of Two Species of Ground Beetles, Pterostichus Melanarius and Harpalus Pensylvanicus (Coleoptera: Carabidae)

Adult carabid beetles of the species Harpalus pensylvanicus (DeGeer) and Pterostichus melanarius (Illiger) were collected from a cultivated field near London, Ont., and brought into the laboratory for observation and mass culture in terraria; the culture method is described. Both species oviposited successfully in the laboratory; P. melanarius produced as many as 134 eggs/female over a 6-month period, whereas H. pensylvanicus deposited only about 10 eggs/female under similar conditions. However, percentage emergence in Harpalus was substantially higher (62.6) than with Pterostichus (36.8 and 45.7). Large numbers of first- and second-instar P. melanarius larvae may be obtained by using the rearing method described. The low oviposition rate of H. pensylvanicus made large-scale rearing of this species difficult. Observations are made on the mating behaviour and adult parasitization by horsehair worms (Nematomorpha) of Pterostichus.