Effects of Fenitrothion(Sumithion[○!R]) Spraying on the Population Density and the Blood Cholinesterase Activity of the Japanese Wood Mounse, Apodemus speciosus TEMMINK

Effect of fenitrothion spraying on the Japanese wood mouse, Apodemus speciosus T. inhabiting two fenitrothion spraying areas was assessed on the basis of population and theirblood cholinesterase activity; Yachimata, Chiba Pref. sprayed from 1976 to 1979 and Kukisaki, Ibaraki Pref. sprayed only in 1979. In both areas, fenitrothion was applied two times annually at the rate of 1.2 kg/ha by helicopter from May to July. No other small mammals except Japanese wood mouse was found in any plot of either area. Probable average densities of the mouse were 28/ha in Yachimata area and 44/ha in Kukisaki area. It was found that they fed on lepidopterous or colepterous insects especially in this season through microscopic observation in their stomach content although they feed mainly on seed for most of the year. Also it appears that among these insects, there are many insects dropped by fenitrothion. No decrease in cholinesterase activities of plasma and erythrocyte of the mouse inhabiting either fenitrothion spraying area during and after application was found.