100 



H. E. EWING. 



shorter fast and were placed back on their succulent wheat shoots 

 in order that they might complete their development. Of those 

 in lot I, 2 individuals reached maturity, and of those in lot 2, 4 

 individuals reached maturity. The average time required for 

 the individuals of these two lots to reach maturity was 5 days in 

 both cases. Quite normal. They were all wingless forms, and 

 gave the following measurements for length: Lot I, i.oo mm. and 

 0.89 mm.; lot 2, 0.96 mm., 0.99 mm., 0.97 mm., and i.oo mm. 

 The mean lengths for the two lots were: Lot I, 0.945 mm.; lot 2, 

 0.980 mm. Both are much bleow the mean for the line. 



TABLE XII. 



DATA FOR EXPERIMENT ON EFFECT OF SINGLE FASTING PERIODS ON SIZE OF ADULTS. 



TAELE XII. Continued. 



From this we conclude that single fasts during the development 

 of Aphis avence Fab. do not necesarily change the length of the 

 period of development, but greatly reduce the size of the adult 

 individuals produced. Data for this fasting experiment are 

 given in tabular form in Table XII. It will be noticed that all 

 the individuals produced in this experiment were wingless forms. 



THE RANGE AND NATURE OF VARIATION IN A PARTHENOGENETIC 



PURE LINE. 



Variation in a parthenogenetic pure line presents all the 

 essential features that it does in nature in general. Probably 

 the one thing that impresses one more than anything else in 



