Notes on the weevils Tyloderma, Auleutes, and Onychylis that feed on Ludwigia and other aquatic plants in southern South America.

Adults of the weevils Tyloderma spp. A and B and Auleutes bosqi (Hustache) fed on the leaves of Ludwigia peploides (H.B.K.) Raven (water primrose) and appear to have it as their only host plant. They fed only on L. peploides in laboratory tests and were collected only from this plant in the field. Onychylis sp. nr. nitrirostris (Boheman) was collected from L. peploides, Eichhornia crassipes (Mart.) Solms (waterhyacinth), and Pistia stratiotes L. (waterlettuce) in the field; in the laboratory it fed on L. peploides, P. stratiotes, and Limnobium stoloniferum (G.F.W. Meyer) Griseb. (frogbit), but not on E. crassipes. The larvae of Tyloderma sp. A and of 0. sp. nr. nigrirostris were probably stem borers, but the larvae of A. bosqi fed on the leaves. All 4 species of weevils could be candidates for biological control of these aquatic weeds in the United States and other countries. Several species of the aquatic plant genus, Ludwigia (water primrose) are aquatic weeds of economic importance in the southeastern United States (Weldon et al. 1969). Some of these pest species have been introduced from other countries and some are native in the U.S. The genus is also native in South America, and Cabrera (1965) recorded 7 species of Ludwigia (=Jussiaea) in Buenos Aires Province, Argentina. We found several species of weevils that fed on Ludwigia peploides (H.B.K.) Raven in Argentina, none of which occur in North America; they are Tyloderma spp. A and B,4 Auleutes bosqi Hustache, and Onychylis sp. nr. nigrirostris (Boheman). Cordo and DeLoach (1982) found a flea beetle, Lysathiaflavipes (Boheman), that heavily damaged Ludwigia in Argentina. These insects could be used in a biological control program if they prove sufficiently host specific to introduce. Wibmer (1981), in his revision named 30 species of Tyloderma north of Mexico. Little is known of their biologies and host ranges. Four species probably have Ludwigia as their host plant (Wibmer 1981). Blackwelder (1947) listed 25 species of Tyloderma south of the United States, 6 of them from Argentina, 2 from Brazil, 2 from the Caribbean, 1 from Venezuela, and the rest from Mexico and Central America. ' Coleoptera: Curculionidae. 2 Accepted for publication February 12, 1982. 3 Present address of the junior author: Grassland, Soil and Water Research Laboratory, ARS, USDA, P.O. Box 748, Temple TX 76503. 4Determined by C. W. O'Brien, Florida A&M University, Tallahassee, FL 32307.