A NUTRITIONAL STUDY OF INSECTS 



29 



period before transfoniiing. Therefore, the pupal period is not 

 correlated with the length of the larval life, i.e., it has, also, a 

 fixed periodicity. 



The growth of insect larvae may be retarded on sterile fruit 

 and then greatly accelerated by adding living yeast cells to the 

 food. Three curves showing this effect are drawn in figure 9 

 and curve A 24, figure 2 has already been referred to (p. 13). 

 The insect can be maintained for a long period of time on a 

 minimum of protein (banana) at the same size or slowly increasing 



,| .| 4 4 4 -\ A B\ s\ ,>o 



Fig. 9 The growth of retarded larvae. 1, larvae from hot aqueous extract of 

 banana placed on 4 per cent yeast on eighth day; 2, larvae from hot aqueous ex-- 

 tract of banana placed on 9 per cent yeast on fourteenth day; 3, larvae from cold 

 aqueous extract of banana, living yeast introduced on twenty-sixth day. 



size, after which it may be made to develop to normal size by 

 placing on an adequate diet (6 per cent yeast) . Except in one 

 case (fig, 9, curve 3) the acceleration in the growth of retarded 

 individuals was not above the normal rate of larvae on an ade- 

 quate diet. This may be due to the fact that the length of the 

 larva is a poor criterion of the extent of its development and that 

 units of one day are not accurate for an animal with a normal 

 larval period of about six days. 



In this connection it is of interest that Osborne and Mendel 

 ('14) have shown that rats can be kept for a long period at the 



