Foraging parameters of two ant species, Pseudomyrtnex triplarinus and Crematogaster sp., on P. triplarinus-occupied shrubs of Triplaris surinamensis were evaluated in a semi-deciduous forest of Mato Grosso, western Brazil. Live workers of the termite Microcerotermes strunckii, used as baits for ants, were placed on leaves in the lower, medium and upper thirds of the crown of thirty experimental Triplaris (nine baits/plant). Besides attacking more than twice as many baits as Crematogaster (131 against 59), Pseudomyrmex also attacked them significantly faster. Pseudomyrmex patrolled the plant uniformly, while Crematogaster patrolled more intensively the lower portion of the crown of Triplaris. Baits retrieved by Pseudomyrtnex were taken to their nests in the stem galleries of Triplaris; those retrieved by Crematogaster were carried to nearby nests in the forest understory. Greater aggressiveness and alertness to foreign objects (i.e. baits), better eyesight, larger size, and an individual foraging technique appear to be responsible for the greater foraging success of Pseudomyrmex when compared with Crematogaster. © 1987, Cambridge University Press. All rights reserved.