Chaenusa aurantium Kula and Martinez, new species and Chaenusa steineri Kula, new species, both from the Neotropical Region, are described. The former species was reared from an undescribed species of Hydrellia Robineau-Desvoidy (Diptera: Ephydridae) in Argentina under evaluation for control of Egeria densa (Planch.) (Alismatales: Hydrocharitaceae), Brazilian waterweed, in the United States. Chaenusa pallidinervis (Brèthes), also from the Neotropical Region, is redescribed. New distribution records are reported for Chaenusa americana (Riegel), Chaenusa bergi (Riegel), Chaenusa quadriceps (Ashmead), Chaenusa trumani Kula, Chaenusa whartoni Kula, and Chaenusa woolleyi Kula from the Nearctic Region, as well as Chaenusa ireneae Kula from the Neotropical Region. These data supplement a recently published revision of New World Chaenusa Haliday sensu lato.