PHYSIOLOGY OF WING DEVELOPMENT IN APHIDS. IO5 



TABLE III. 



V. STRENGTH OF MAGNESIUM SULPHATE NEEDED TO PRODUCE 



THE WINGED APHIDS. 



It must be conceded that no accurate methods of measuring 

 the amount of any solution can be devised, for the reason that 

 the solution must first pass through the plant tissue before it 

 reaches the body of the insect. For the purpose of obtaining 



