FACTORS AFFECTING MOSQUITO LARVAL ABUNDANCE AND SURVIVAL IN NORTHERN CALIFORNIA RICE FIELDS (CULEX TARSALIS, ANOPHELES FREEBORNI, ELISA, PREDATORS)

Factors affecting the dynamics of larval populations of Culex tarsalis and Anopheles freeborni in northern California rice fields were studied from 1982 to 1985. Larval abundance was monitored using a standard mosquito dipper. Larval survival and development were evaluated with predator exclusion sentinel cages and by estimating life table attributes.;No difference in native mosquito larval abundance was seen between geographical areas (south Sutter county or north Yuba county), field age (first year planted in rice or previous year planted in rice), water source (surface or well), field preparation (laser planed or contour levees), water depth (shallow, medium, deep or deep with drain).;In general, fields productive for mosquito larvae had high levels of electrolytes (as reflected in conductivity measurements) and greater species richness.;Microturbellarian flatworms, Mesostoma sp., can effect 100% larval mortality in sentinel cages but the extent of their influence in the natural system was not quantified. Efforts to rear this flatworm in the laboratory were not successful. Of the collection techniques examined, dipping with a standard mosquito dipper provided the most consistent results for collecting Mesostoma from rice fields.;Life table studies indicated 90-95% mortality for both species from first instar to pupae. Numerous factors that may contribute to this mortality were examined.;For insect predators, predator prey relationships in the rice field were evaluated using an Enzyme Immunoassay (EIA). Of the field collected predators tested, 18% of the Belostomatidae, 18% of the Coenagrionidae and 4% of the Laccophilus (larvae) were positive for mosquito larval proteins in their gut contents.