This common ground beetle is widely distributed. It is a voracious predator with a varied diet which includes: springtails, earthworms, aphids, slugs, and flies. This species comes in two forms: a short-winged flightless (brachypterous), and long-winged flying (macropterous). Long-winged individuals play an important role in helping this species colonise novel habitats.
During my undergraduate years, I researched the ability of P. melanarius to control blueberry maggot infestations. Blueberry maggots develop within a single berry, leaving the berry to pupate within the soil. It is this stage when the pest is most most vulnerable to predation. In laboratory experiments, we found that addition of a single beetle was able to reduce the number of pupae between 40-80% relative to a control.
Bourassa, S., Spence, J. R., Hartley, D. J., & Lee, S. I. 2011. Wing-dimorphism and population expansion of Pterostichus melanarius (Illiger, 1798) at small and large scales in central Alberta, Canada (Coleoptera, Carabidae, Pterostichini). ZooKeys 147: 545.