Carabid beetles were pitfall-trapped in soybean, Glycine max (L.) Merr., fields hosting populations of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in central New York state in July and August 2004 and 2006. Carabids were collected from five fields located in three counties in 2004 and from two fields both located at the same farm in 2006. In total, adults of 60 carabid species were collected, 10 of which represent introductions from Europe. Agonum muelleri (Herbst), a Palearctic native, was the dominant carabid species both years, a role not previously reported in U.S. carabid assemblages. Both years, A. muelleri was the most abundantly trapped species, and it was collected in more than half of the pitfall traps. The majority of carabid individuals trapped, including A. muelleri, belonged to species overwintering as adults. The most common larval overwinterer, the European native Pterostichus melanarius (Illiger), made up only 6.0% (2004) and 5.5% (2006) of the total carabids species caught, yet this species was relatively broadly distributed (in 40.1% of traps in 2004 and 26.0% of traps in 2006). In three no-tillage fields with canopy closure, densities of the seven most common carabid species were high at the beginning of the season, but they decreased in early August as aphid densities began increasing. A significant negative exponential relationship described this relationship between activity density of carabids and aphid density. A no-choice feeding assay confirmed that the dominant species A. muelleri readily eats soybean aphids, which is consistent with carabid predation on soybean aphid populations. Pitfall traps were arrayed to allow comparisons of carabid beetle distributions among field edges, and distances 10 and 20 m into fields. Among the seven most common species, significantly more adults of A. muelleri, Poecilus chalcites (Say), Poecilus lucublandus (Say), and Pt. melanarius were trapped within fields compared with at field edges.
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Vol. 100 • No. 6