Abstract: The effective factors causing the production of alatae in soybean aphid Aphis glycineswere studied in the laboratory. The result shows that crowding of adult apterae plays a main role in the production of alatae, but nymphal apterae are not sensitive to crowding. Although more alatae will be produced when crowding is intensified in colonies of low population, the responses decrease with the overcrowding condition. The quality of soybean leaves is not afactor determining the production of alatae, btu it may change the response of the crowded apterae females to crowding. Aphids starved for 24 hours in isolation give no response to the soybean leaf quality. Temperature and parentage are other factors influencing the propor tion of ala, ae in the progeny of the apterous females. Higher temperature depresses the appearance of winged aphids through the embryo within the apterous females The ala'ae are less sensitive to crowding than the apterae.

Key words: Aphis glycines——alary dimorphism——crowding——host plant qu- lity——temperature