101 



THE EXPERIMENTAL PRODUCTION OF WINGED 

 FORMS IN AN APHID, MYZUS RIBIS, LINN. 



By maud D. HAVILAND, 



Research Fellow, Newnham College. 



It is well known that most Aphidini are dimorphic in respect of the 

 viviparous parthenogenetic generations, which may be either winged or 

 wingless; but the appearance of either form is determined by factors not 

 yet understood. Failure of the food supply has been suggested by some 

 authorities, but this view is based on general observation rather than 

 on experiment. B6rner(i) points out that in autumn Rhopalosiphum 

 lactucae produces a host of apterous females whose attack causes the 

 plant to sicken and die, and yet no winged forms appear. He also records 

 some observations on the " hop louse," where a healthy plant produced 

 more alate females than a sickly one. 



In 1901 Clarke (2) cultivated the common rose aphis upon cuttings 

 planted in sand saturated with solutions of various salts, and he recorded 

 that a solution of magnesium salts resulted in the development of an 

 abnormally high proportion of winged forms. I have not been able to 

 obtain a copy of Clarke's paper, but his experiment was repeated in 1912 

 by Neiills(5) with similar results, and has since been ampHfied and ex- 

 tended by Shinji{6). 



Shinji experimented with several species of aphides, and found that 

 by watering the host-plants with solutions of certain substances, the 

 proportion of winged forms produced might be as much as 100 per cent. 

 He also records that other solutions had a contrary effect. 



Among the "wing-producing substances" are included salts of mag- 

 nesium, antimony, nickle, tin, zinc, and also sugar; while the list of 

 "non-wing producing substances" contains tap- water, alcohol, tannin, 

 urea, and salts of strontium, potassium, and calcium, etc. The aphides 

 were susceptible to the treatment for three or more days after birth, 

 according to the species. 



In 1920, I had occasion to rear a number of generations of the red 

 currant aphis [Myzus rihis) in connection with a statistical inquiry into 

 variation. As the required characters appeared only in the winged female, 



