Sameodes albiguttalis(Warren) is highly specific to the plant family Pontederiaceae. In laboratory tests, it laid 60.3% of 13,645 eggs on waterhyacinth, (Eichhornia crassipes(Mart.) Solms), and 33.3% on 3 other species of Pontederiaceae; a few eggs were laid on 12 other plants of the 46 species tested. Larvae completed their development and produced adults or pupae only on waterhyacinth or occasionally onEichhornia azurea(Swartz) Kunth andPontederia cordataL. in the laboratory. However, in the field, larvae and pupae ofS. albiguttaliswere collected only from waterhyacinth and occasionally fromE. azurea.Sameodes albiguttalishas never been reported in Argentina onP. cordataor as a pest of any beneficial plant, and it did not damage any beneficial plants tested (exceptP. cordatain the laboratory). It appears safe for introduction into the U.S. to control waterhyacinth.