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A microsporidan, Thelohania sp., was isolated from workers of the black imported fire ant, Solenopsis richteri Forel, in Montevideo, Uruguay, and Las Flores, Argentina, and from a Solenopsis sp. in Montevideo, in March and May of 1974. Many of the colonies exhibiting high levels of infection in March were abandoned or drastically reduced in size when re-examined in May. No disease was observed in populations of S. blumi Buren or S. quinquecuspis Forel.

A method was developed for determining the number of cadavers of the velvetbean caterpillar, Anticarsia gemmatalis (Hubner), infected with the fungal pathogen Nomuraea rileyi (Farlow) Samson in the developmental stage just prior to conidia formation (white stage) in a soybean field. One-third of the total number of cadavers in this developmental stage were observed to fall on the shake cloth during population sampling; (approximately two-thirds remained on the plant). Estimates of white cadaver counts from laboratory-held lots of field-collected larvae did not correlate with actual field counts.

Reinfectivity studies were conducted on late instar lovebug larvae, Plecia nearctica Hardy (Diptera-Bibionidae), inoculated with Tolypocladium cylindrosporum Gams, Metarhizium anisopliae (Metch.) Sor. and Beauveria bassiana (Bals.) Vuill. which were isolated and identified from dead larvae. Two tests demonstrated that each fungus apparently affected larval mortality; however, data analyses indicated that only B. bassiana caused significant mortality levels (27% to 33%). Problems related to reinfectivity tests are discussed. Nine additional fungi are reported from dead and moribund larvae collected in the field.

Populations of Plecia nearctica Hardy were surveyed during the spring and fall of 1973 to monitor adult flights which usually occur in May and September. The May adult flight was noticeably smaller. A large flight was observed in September. During early spring, 5 species of fungi were isolated and identified from dead and moribund lovebug larvae collected in the Gainesville area. In the fall, 2 additional fungal species were isolated, 1 from adults during the September flight and 1 from laboratory reared larvae.

An epizootic caused by the entomogenous fungus Spicaria rileyi (Farlow) occurred among populations of the velvetbean caterpillar, Anticarsia gemmatalis Hubner on soybeans, Glycine soja, Sieb. and Zucc. in August and September 1970. The natural outbreak was monitored in Quincy where environmental conditions favoring development of the fungus prevailed during July through September. The development of the epizootic was related to the build-up of insect populations, and the development and dissemination of the fungus.