The fire ants of the Solenopsis geminata species-group of Trager (1991) are revised based on the morphology of worker larvae and of adult forms of workers, males, and gynes (winged or dealated members of the queen caste). The amount of intraspecific variation occurring in the adult males and gynes was equivalent to that of workers, making the taxonomic information gained from these castes no better than information from the workers. A new species, S. metallica, is described from southern Brazil, based on adult workers, adult gynes, males, and worker larvae. The following classification changes are made: S. virulens is placed in the S. virulens species-group; S. tridens and S. substituta are placed in the S. tridens species-group; S. metallica new species, S. daguerrei, S. electra, S. hostilis, S. interrupta, S. invicta, S. macdonaghi, S. megergates, S. pusillignis, S. pythia, S. quinquecuspis, S. richteri, S. saevissima, and S. weyrauchi are placed in the S. saevissima species-group; and S. geminata, S. xyloni, S. amblychila, S. aurea, S. gayi, and S. bruesi are left in the S. geminata species-group. The older classification, which designated complexes and subcomplexes, is abandoned. For the S. saevissima species-group, adults of males and gynes, as well as worker larvae, are described and diagnosed for each species. Diagnoses and keys (dichotomous and tabular) are provided for adult workers, the most commonly collected material, and distributions of the species are summarized.