Several South American species of Pseudacteon have been released for biocontrol of red imported fire ants Solenopsis invicta in the U.S. Here we provide additional data from host specificity tests on 4 additional candidate species, P. nocens, P. nudicornis, P. cultellatus, and P. obtusus, all of which are components of multi-species complexes that occur within Argentinean Solenopsis populations. All 4 species were tested with sequential, no choice exposures to the red imported fire ant S. invicta, and the tropical fire ant, S. geminata. Levels of intra-generic specificity ranged from moderate to high and all 4 species showed greater specificity than some Pseudacteon species already approved for release.