EFFECT OF STARVATION ON WING DEVELOPMENT. 303 



, 

 removed from the plants as soon as it was possible to determine 



the presence or absence of wing buds. 



It has been suggested that young produced in the early part 

 of the reproductive life of the mother would be better nourished 

 and fewer wings would develop than among those born at the 

 end of the period of reproduction. A consideration of the Ai 

 and A2 series of Table I. seems to disprove this, as more wings 

 developed in the families of the older members. 



It might also be suggested that the effect of starvation was 

 to reduce the size of the families and consequently the percentage 

 of winged forms might be raised. In some cases the size of 

 families of the starved mothers was smaller than that of the 

 control, in other cases it was greater. The average sized family 

 was 50.2 in the starved lines and 52.2 in the controls. The differ- 

 ence is not large enough to be important. 



A few experiments were carried on with starved winged 

 mothers. These are difficult to obtain, since the number normally 

 produced is low and since it is impossible to distinguish wing 

 buds at the early period when starvation is begun, thus the 

 chances for finding winged forms among the starved young are 

 slight. The control experiments (Table IV.), show that of the 

 young of five winged mothers only 3 per cent, were winged. 

 In the few families of starved winged mothers the percentage 

 is less, often none of the young develop wings In passing it 

 might be noted that in the G series (Table IV.) no. 5 and no. 6 

 winged individuals starved 45 hours produced no winged young, 

 while their wingless sisters nos. 2, 8, 9, produced 29 per cent. 

 winged forms. Apparently starvation has little effect on winged 

 mothers. Teleologically this result would be expected. There 

 would be no need for more winged forms in nature, since the 

 parent had migrated to a fresh food supply. 



In conclusion it seems most probable that the lessening of 

 the food supply is the primary factor in determining the develop- 

 ment of wings in the offspring of wingless mothers. The wing 

 anlage appears to be present in all the parthenogenetic females 

 and depends directly upon the condition of the food supply of 

 the mother for its stimulation or suppression of development. 



COLUMBIA UNIVERSITY, 

 June, 1916. 



