PHYSIOLOGY OF WING DEVELOPMENT IN APHIDS. 97 



Before going further, the writer wishes to acknowledge his 

 indebtedness to Professor Woodworth, at whose suggestion the 

 work was begun. His hearty thanks are also due to Professor 

 E. Van Dyke, who, jointly with Professor Woodworth, gave 

 valuable criticism and helpful suggestions during the progress of 

 the investigation. 



II. EXPERIMENTS WITH THE ROSE APHID. 



These were partly to verify the findings of Professor Clarke 

 and partly to make a more extensive test of the action of chemi- 

 cals. The method of experimentation was that adopted and 

 carried out by Professor Clarke. Sharp, clean sand was washed 

 several times in running water, and then left to soak over night. 

 The following day it was washed again with distilled water and 

 after drying was ready for use. Four-ounce tumblers were then 

 filled to one half of their depth with this sand and moistened with 

 solutions of various chemicals. In each of these tumblers, a 

 rose twig bearing from one to three viviparous females, usually 

 apterous, was planted. Though Mr. Neiils pointed out the fact 

 that three days are usually required for the magnesium salts to 

 produce the largest number of winged aphids, it is not always 

 necessary that the mother aphids be transferred to the twig that 

 number of days after it is planted, to see the effect of the salts, 

 for, as is also stated by Mr. Neiils, the young aphids become 

 winged if they are subjected to magnesium salts within three 

 days after birth. Consequently, I used the method previously 

 described. A careful watch was kept of the twigs and when 

 winged forms appeared, they were taken away, and the records 

 kept of their appearance, as well as of the total number of young 

 born. In my later experiments, the record was taken only 

 once, when the first born had acquired the wings, because I had 

 found that the tendency of the young aphids to produce wings 

 could be accurately determined a certain number of days after 

 birth. 



I had thought that some other substances might also produce 

 winged aphids. This belief was suddenly strengthened when I 

 found, late in November, that a rose twig that was planted in an 

 old tin can containing ordinary water, was infested with 126 



