Pterostichus melanarius, the rain beetle, is a type of carabid (ground beetle) of the genus Pterostichus. It is native to Europe but is increasingly found in North America after being introduced to the region in the 1920s. It is a predatory beetle that eats other invertebrates, which makes it a valuable pest control agent in agricultural settings. Additionally, the beetle has wing dimorphism which has contributed to its increasing distribution across North America.

The larvae of this species of beetle have been observed exhibiting cannibalistic behaviorisms in high population densities. The rain beetle's habitat is influenced by their hunger level, with starved beetles preferring larger prey ranges compared to satiated beetles.

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