98 GEORGE O. SHINJI. 



winged and 2 apterous forms. This, I thought, was due to the 

 presence of either tin or iron, because ordinary water, as will be 

 seen elsewhere in the table, never produces more than 5 per cent, 

 of winged forms. Consequently, I tested several salt solutions 

 of the heavier metals and obtained the result's which not only 

 confirmed my belief, but also incidentally led to the finding of 

 several new salts which could develop winged aphids. 



Sugar and urea were also used in order to determine the effect 

 of electrolytes as well as osmotic pressure. Urea never, or very 

 rarely, produced winged individuals. The action of cane sugar 

 caused rather confusing results, because the young ones produced 

 on twigs, placed in the sugar solution that had been standing for 

 a few days, remained apterous, while those on twigs in fresh 

 sugar solution produced winged forms. These apparantly con- 

 tradictory results, it was first thought, might be due to the decom- 

 position of sugar by fermentation. That this explanation may 

 be correct is indicated by the fact that both alcohol and acetic 

 acid always produced apterous forms. From December 8th on, 

 the practice was followed of transferring the twig to a fresh 

 solution every three days with uniform results. 



When a stronger solution, about m/2O of strontium bromide or 

 strontium chloride was used, the tips of the twigs would dry out 

 in the course of from 36 to 48 hours. Many aphids would fall off 

 the twigs; those staying on the twigs would change to a dark 

 salmon color, lose water, and finally dry upon the twig. Even 

 in a solution of m/ioo-m/^oo of strontium bromide, the twigs 

 planted in it became darker in color and emitted the characteristic 

 odor of strontium salts. About 99 per cent, of the young aphids 

 remaining on the twig developed no wings. 



Calcium chloride produced the same, but a weaker effect on 

 the twig and also on the aphids. All aphids stayed on the twig 

 charged with m/$o solution of the salt, but remained apterous. 



Owing to the very .poisonous nature of the chemicals used, 

 often the entire number of the young born on a twig charged with 

 the solutions of mercury, lead or copper salts, would drop off 

 before it could be determined whether they were winged or not. 

 But the fact that some of them, happening to remain long enough, 

 produced wings indicated that the solution had the wing-develop- 



