Diversity and seasonal density of carabid beetles (Coleoptera: Carabidae) in relation to the soybean aphid in soybean crop in Québec, Canada

AbstractWe studied the diversity and summer seasonal activity-density of Carabidae associated with soybean fields infested by the soybean aphid (Aphis glycinesMatsumura; Hemiptera: Aphididae) in Québec, Canada. Carabid beetles were sampled in six to seven fields from June to September 2004 and 2005 using pitfall traps. A total of 33 species from 15 genera were identified, with the exotic Pterostichus melanarius(Illiger) (Coleoptera: Carabidae), representing 75.8% and 84.5% of all individuals trapped in 2004 and 2005, respectively. Large variations in species richness and diversity indexes were observed between fields within and between years. Multivariate analyses showed that carabid activity-density varied as a function of field location and sampling period, with individuals belonging to species overwintering as adults being more abundant early in the growing season. There was no relationship between carabid trap catches and A. glycinesdensity, suggesting that carabid beetles do not respond numerically to soybean aphid populations at the spatial scale studied.