Technical Abstract: Larvae of eleven species of picture-winged flies (Diptera: Ulidiidae) are known to feed on corn plants (Zea mays L.) in the western hemisphere. Choice and no-choice tests were conducted in greenhouse and field trials to determine the pest status on sweet corn of three of these species found in Florida: Chaetopsis massyla (Walker), Euxesta eluta Loew, and E. stigmatias Loew (Diptera: Ulidiidae). The experiments were set up as split-plot designs with three levels of ear infestation as the main treatments [uninfested, infested with Spodoptera frugiperda (Lepidoptera: Noctuidae) or E. eluta larvae] and subsequent exposure to C. massyla, E. eluta, or E. stigmatias adults as the sub-treatments. Ears were exposed to the sub-treatments to allow oviposition for 10 d following first silk and the resulting infested ears were harvested and held for adult emergence. All three species were reared from uninfested and both types of infested ears in both choice and no-choice tests in greenhouse and field trials confirming both primary and secondary modes of ear infestation. More flies of all three species emerged from corn ears that were pre-infested with S. frugiperda than uninfested corn ears suggesting either preference for or greater survival within ears previously infested with such larvae. Fewer E. stigmatias and C. massyla adults emerged from ears pre-infested with E. eluta in no-choice tests suggesting that previous infestation by this fly may negatively affect oviposition or that older fly larvae affect survival of neonate larvae. All three species studied here should be considered primary pests that can render unprotected sweet corn ears unmarketable.