Gut Contents of Ground Beetles (Col., Carabidae), and Activity of these and other Epigeal Predators during an Outbreak ofRhopalosiphum padi(Hom., Aphididae)

Abstract

Abstract Polyphagous ground beetles were collected with pitfall traps from a spring barley field during an outbreak of Rhopalosiphum padi (L.) in southern Finland. A total of 1175 specimens belonging to 29 species of Carabidae were caught during a five-week trapping period, which gave an average of 0.68 specimens per trap day. Carabids together with staphylinids were more numerous than spiders. Bembidion guttula was the dominant species, but Clivinafossor and Bembidion quadrimaculatum also occurred abundantly during the establishment phase of the aphids. Three weeks later, during the population peak of the aphids, Bembidion spp. had declined and Amara plebeja was the most numerous species in the catch Gut dissections showed that Bembidion spp. and C. fossor had predated on R. padi just after the first colonists had arrived. Together with aphids, Collembola and other soil animals comprised the food typical of Bembidion spp. During the aphid peak, a high percentage of A. plebeja and Harpalus rufipes had con...