Abstract: Propreus simulans is a predatory natural enemy of aphids,thrips and leaf spi der mites infesting reed.Field and laboratory observations have revealed that th e predator has two generations a year in the Dongting Lake area,Hunan Province.It overwintered as adult and/or nymph in reed stalks,debris and soil crevices.The longevity of the first generation adults was found to be about four months,whil e that of the second generation adults was ten months including overwintering.The adult sex ratio was 5∶4(male∶female).Mating could occur several times in both sexes during their life span.Each female adult could lay an average of 39.3 eggs during its life.Eggs hatch in 6.5 days.The developmental period of the first generation nymphs was about four months,and that of the second generation was ab out nine months.Main prey species of P.simulans in the Dongting Lake area in clude Melanaphis sp. Fulmekioia serrata,Oligonychus sp., Sesamia sp. Leu cania separate,Chilo niponella and Dimorphopterus spinolae. It was found th at the population fluctuation of the predator was caused mainly by topography(low lands vs high lands),flood,application of chemical pesticides and availability of prey.