BIOLOGICAL CONTROL Phytophagous Insects Associated with Pistia stratiotes in Florida

with Pistia stratiotes L., waterlettuce, in Florida. Plant samples were collected at 61 sites. Samples comprised a minimum of 20 waterlettuce rosettes. Invertebrates were removed from the plant sample using a submergence technique. Eighteen phytophagous species were recovered from P. stratiotes. Six of these species are known waterlettuce feeders. They include the moths Petrophila drumalis (Dyar), Synclita obliteralis (Walker), and Samea multiplicalis Guenee, the aphid Rhopalosiphum nymphaeae L., the leafhopper Draeculacephala inscripta Van Duzee, and the weevil Tanysphyrus lemnae (F.). Most of these insects are either stenophagous or polyphagous; none feed exclusively on waterlet-tuce. The paucity of specialists on waterlettuce in Florida contrasts sharply with the richness of oligophagous species in South America. This suggests that waterlettuce is not a native species, despite observations of its occurrence in Florida as early as the mid-1700s. KEY WORDS Pistia stratiotes, zoogeography, phytophage IN RECENT YEARS, waterlettuce, Pistia stratiotes L., has received a great deal of attention because nuisance levels of the plant interfere with proper use of water resources in many countries (e.g., Holm et al. 1977, Center et al. 1990). Investiga-tions in South America (DeLoach et al. 1979)