In this paper we present a qualitative and quantitative evaluation of the supply and harvest of herbaceous biomass of the Acromyrmex striatus ant at a site in Santa Rosa city, La Pampa province, Argentina (36º28' S 64º35' W). Annual input of green material to the nest was 0,14 kg/year.nest and 0,60 kg/(year.hectare); which is the lowest value reported for species of this genus. In the region studied, Acromyrmex striatus primarily cuts monocotyledonous, harvesting small amounts of all available plants. The presence of Acromyrmex striatus in this semiarid area would not decrease the availability of native grasses preferred by cattle.