This research characterizes the interaction between the fire antsSolenopsis invicta Buren and developing soybean plants.Phagostimulant studies showed that fire ant foraging on soybean seedsincreased once the seeds imbibed water. During seedling developmentover a 5-d germination period, fire ant foraging shifted from thestem/cotyledons to the roots, despite continual increases in freshweights for each region, and the fact that stem/cotyledon tissuecontained the majority of food reserves. Carbohydrate analysis showedthat although 2-d-old seedlings had higher concentrations ofphagostimulant carbohydrates, especially sucrose, than tissues ofmature plants, all tissues analyzed had enough of these sugars toinduce a phagostimulant response. Fire ant association withseeds/seedlings germinated in soil resulted in reduced seedling vigor,as determined by a doubling of seedling emergence time, a threefoldincrease in malformed seedlings, and visible damage to cotyledons.Seeds germinated and grown to mature plants in association with fireants, allocated 43% more assimilate into pods, but produced 28% lessroot dry matter, 11% less total dry matter, and there was an 81%reduction in the number of root nodules compared with control plants.We propose that reduced root development and inhibitions of noduleformation would be major yield limiting factors under field conditions.This work demonstrates that fire ant damage to soybeans is not limitedto seedling establishment and that more research should be directed atthe subterranean activities of the fire ant.