2.Why winged aphides are produced 1)Climate Conditions(气候条件) 2)Host Nutrition(寄主营养) 3)Aphid Population Density(种群密度) 2. Why winged aphides are produced 1) Climate Conditions (气候条件） 2) Host Nutrition (寄主营养 ) 3) Aphid Population Density (种群密度 )