Abstract: Systematic investigations on vegetable aphid population were carried out on 10 crops of Brassica oleracea var.capitata and 23 crops of B.campestris ssp.chinensis during 1990～1992 in the suburbs of Hangzhou.The K value of negative binomial distribution less affected by density was chosen to describe the spatial and temporal patterns of mixed aphid population. The results indicated that the mixed population of Myzus persicae and ipaphis erysimi was aggregated on the two vegetables throughout the year, but the aggregation intensity changed seasonally. The population was highly aggregated from July to September, and two peaks of dispersal was shown on May and November. The intensity of aggregation on Brassica oleracea var. capitata differed between seasons. From spring to summer, the population changed from highly to loosely aggregated, and then, to highly aggregated again, but from summer to autumn, the aggregation intensity was always very high. The temporal pattern of aggregation from autumn to winter differed between years, and the intensity of aggregation increased gradually, and then, fluctuated from winter to spring.The aggregation intensity of L.erysimi was higher than that of M.persicae. With reference to the trade-off of population and the change of environmental factors, the mechanism of the observed spatial patterns was discussed.

Key words: Myzus persicae, Lipaphis erysimi, Population spatial dynamics, Negative binomial distribution, carbon, nitrogen, Loess Plateau, Robinia pseudoacacia, plantation age, phosphorus