Odonalologica 19(4): 359-3(6 December I, 1990 Odonata associated with water lettuce (Pistia stratiotes L.) in South Florida L.P. Lounibos , R.L. Escher , L.B. Dewald N. Nishimura and V.L. Larson Florida Medical Entomology Laboratory, University of Florida, 200 9th St SE, Vero Beach, Florida 32962, United States Received April 10, 1990 / Accepted May 7, 1990 INTRODUCTION The cosmotropical macrophyte Pistia stratiotes L. is known to be an important nursery for aquatic insect life (DUNN, 1934; MACFIE & INGRAM, 1923). Among insect orders found on P. stratiotes in Volta Lake, Ghana, larval Odonata dominatedin biomass and were second to Diptera in absolute numbers (PETR, 1968). Representatives of at least five genera of Anisoptera and three genera of Zygoptera were recovered during Petr’s ten-month study. Larval Anisoptera accounted for approximately ten times more biomass than Zygoptera on Volta Lake, but DRAY et al. (1988) reported that dragonfly larvae were relatively uncommon on water lettuce in Florida. The present paper represents a portion of a two-year study undertaken to identify the aquatic insect fauna on water lettuce at one locality and to describe the relationship between mosquitoes of the genus Mansonia, other members of the insect community, and growth of this host plant (LOUNIBOS & DEWALD, Larval Odon. were identified from quantitative samples of water lettuce made from a single pond. 3 spp. of Zygoptera accounted for more individuals but less biomass than 4 spp. of Anisoptera. Numbers of larvae were highest in the winter when smallest size classes predominated, and lowest in the spring and summer when larger size classes were present. Size class data indicated a probable spring emergence for Telebasis byersi and Pachydiplax longipennis and an autumnal emergence for Coryphaeschna adnexa. Foregut dissections of freshly caught larvae revealed iden- tifiable remains of certain prey, the commonest being larvae of Mansonia mosquitoes which attach to roots of P. stratiotes.