( 1 ) Iwao (1968) proposed a regression method (i. e. Iwao's patchiness Regression).It assumes that mean crowding (m) is linearly related to mean density (m) as followsThe m m relationship was examined by the population data of the nymph Nilaparvatalugens in 1979 and 1981. The regression equation is m = 1.00 + 1.37 m( 2 ) The values of α and β from that regression equation and 5 per hill serve as the critical density was substituted to the equation of Iwao's sequential sampling. The upper limit of the seque...