THE EFFECT OF STARVATION ON THE WING 



DEVELOPMENT OF MICROSIPHUM 



DESTRUCTOR. 



LOUISE H. GREGORY. 



As is the case with aphids in general, the life history of Micro- 

 siphum destructor, the green pea-aphid, shows a definite relation 

 to the environment. Dimorphism is common. Winged and 

 wingless individuals appear in varying numbers at different 

 stages in the life history, the wingless forms predominating in 

 the early part of the reproductive history, the winged forms 

 increasing in number toward the end of the summer. \Vhile 

 it is generally accepted that external conditions probably control 

 the appearance of wings, very little data has been offered as proof. 

 For a number of years, at the suggestion of Professor Morgan, 

 I have experimented with the effect of starvation on the pro- 

 duction of winged forms in the families of the green pea-aphid. 

 I am glad to express my appreciation of Professor Morgan's 

 helpful criticisms. 



In starting all experiments, a single individual, selected to 

 produce the stock family, was isolated on a young pea plant in a 

 small pot and covered with a lamp chimney, the top of which 

 was covered with gauze to prevent the escape of the aphid and 

 the confusion of families. This method of isolation was used 

 throughout the investigation and proved most successful, the 

 plants growing normally, sufficient air entering at the top of the 

 chimney. From the family of the stock aphid, some young were 

 isolated and used as control lines, others were removed daily 

 from the plant and starved for periods of different lengths, 

 twenty-four hours, twelve hours and eight hours. Experience 

 proved that fewer deaths resulted if the aphids were starved 

 eight hours daily. After the period of fasting the starved aphids 

 were isolated and their offspring observed. As will be clear 

 later, the effect of starvation on wing development is not apparent 

 in the individuals starved, but in their offspring. 



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