IO2 GEORGE O. SHINJI. 



The above results not only verified the findings of Professor 

 Clarke, but also led to the discovery of new substances. In 

 addition to the magnesium salts, salts of antimony, nickle, tin, 

 mercury, lead, zinc and also sugar were found to produce winged 

 aphids; while alcohol, acetic acid, alum, tannin, salts of stron- 

 tium, potassium and calcium, and also urea were shown to have 

 no effect. These substances may, therefore, be classified into 

 wing-developing and non wing-developing substances, respec- 

 tively, according to their action on the wing buds. To the 

 former class, belong the salts of alkalis and the alkaline earths, 

 while to the latter belong all of the other salts mentioned, as well 

 as sugar. 



III. EXPERIMENTS WITH OTHER SPECIES OF APHIDS. 



The studies thus far mentioned concerned only the common 

 rose aphis. Do these substances have a similar effect upon 

 other species of aphids? I, therefore, instituted another series 

 of experiments, using the same methods as were employed in the 

 course of the development in the rose aphid. 



The following results were obtained (Table II.): 



As is shown in this table, the results obtained with these 

 aphids are not different from those obtained with the rose aphids, 

 i. e., alkali salts and salts of alkaline earth, together with dis- 

 tilled water, tannin, alcohol and acetic acid produced no winged 

 aphids, while the rest of the salts and also sugar produced winged 

 forms in these species, as they did in the rose aphids. 



The periwinkle aphids, as will be noticed in the table, never 

 yielded one hundred per cent, of winged individuals with ordi- 

 nary strengths of wing-producing substances; e. g., a fifteen per 

 cent, solution of sugar or m/^o of magnesium sulphate. Sub- 

 jection to a very weak solution of the alkali salts, or even to dis- 

 tilled water, did, on the other hand, completely suppress the devel- 

 opment of the wings. Thus, although the number of the winged 

 forms produced on twigs charged with wing-producing sub- 

 stances was small, their appearance must be accredited to the 

 presence of these substances. The common aphids on Sonchus, 

 on the mustard and on the German ivy (Senecio sp.) were found 

 to develop their wings after subjection to very weak solutions of 



