The ground -dwelling insect community was studied in a Natural Reserve of semiarid Chaco Forest, inCentral Argentina. Five collections were made between MarchI992- December 1993, each consisting of 60randomly placed pitfall traps. Coleóptera and Díptera were the most important orders, in terms of both familyrichness and number of individuáis. The species composition of Coleóptera was analyzed, Tenebrionidaebeing the most diverse and abundant family, while Carabidae was remarkably poor.The trophic structure of the system was dominated by scavengers. These represented the richest and mostabundant feeding guild, for the insect community in general and for Coleóptera in particular.