THE B VITAMIN REQUIREMENTS OF ANIMALS AND PLANTS 313 



choline. 21 Such responses, however, must be assessed in terms not only 

 of weight, but also of the time required to reach the adult stage, and the 

 number of nymphs surviving. Indeed some workers use the product of 

 the number of insects reaching a certain stage of development and the 

 reciprocal of the average time required to reach that stage as a criterion 



Day*. 



Figure 3. Increase in pyruvic acid in Corcyra cephalonica St. larvae on a thiamine 



deficient diet. Ten larvae were used in each test group. Pyruvic Acid is in mg per 



100 gm of larvae. 



of response. 18 Certain interesting conclusions are apparent when such a 

 criterion is applied to some of Fraenkel and Blewett's data, 17 as shown 

 in Table 18. Species differences are readily apparent, as witness the 

 critical nature of riboflavin for Ptinus. Certainly riboflavin, niacin, and 

 pantothenic acid stand out for these three species as the B vitamins most 

 critically required in their nutrition. 



