During 1918, observations near Lonoke, Ark., extending over the entire rice-growing season from June to September inclusive, indicated the general prevalence of the following conditions: Anopheles breeds within the rice fields in about equal quantities with Culex, both being found in moderate abundance. Breeding occurs with fair uniformity over the entire field, with slight preference shown for the more open water along levees. Breeding of both Anopheles and Culex begins ten days or two weeks after fields are flooded, and continues, with some variations, until late in September, when it diminishes gradually. Top-minnows in the fields are to be found usually along the levees or at the water inlet, but rarely are they seen in midfield. Predatory insect larvae, principally Hydrophilus, Dytiscus and certain Odonata (damsel-flies), are usually abundant enough to constitute a probable factor in the natural destruction of mosquito larvae. The foregoing observations are based on standardized and comparable examinations,