Water from a mosquito larval habitat in Florida was collected periodically for one year. After removing debris and macroscopic organisms, the small particles were concentrated by continuous flow centrifugation and examined microscopically. Anopheles quadrimaculatus, Culex salinarius and Heliothis zea larvae were exposed to the concentrates. The microsporidia isolated were Nosema, Pleistophora, Telomyxa, Vavraia and Vairimorpha. In addition to these microsporidia, a Helicosporidium (Protozoa), a Metarrhyzium (fungi) and two cytoplasmic polyhedrosis viruses were also isolated.