A NUTRITIONAL STUDY OF INSECTS 



15 



size in four or five days, while larvae on sterile banana (A) did not 

 reach their maximum size in twenty-eight days. 



The minimum requirement of yeast was* found by the use of 

 media consisting of 1, 2, 3, 4, 6, 9, 12, and 24 grams of yeast, re- 

 spectively, separated in 100 cc. of water and thickened with pow- 

 dered agar-agar. On sterile 1 per cent yeast the larvae grew very 

 slowly for twenty days, dying at a length of 4 mm. without pu- 

 pating. On sterile 2 per cent yeast larvae pupated when 5.5 mm. 

 in length, reaching this size on the lOth day. On 3, 4, 6, 9, and 

 12 per cent yeast media the results were much alike, the larvae 



Fig. 3 Larval growth on dead yeast. W 3, 4, 5, show rapid growth on dead 

 yeast; A. shows slow growth on sterile banana. 



reaching a size of 7.5 to 8 mm. in length on the third, fourth, or 

 fifth day and pupating before the eighth day. On 24 per cent 

 yeast the larvae often reached a length of 6.5 mm. on the first or 

 second and pupated before the sixth day. 



Records of the growth of cultures of larvae, on yeast media 

 of different strengths, follow in table 4 and the mean lan^al 

 periods are included in table 5. In figure 4, curve 1 shows the 

 rapid growth on 24 per cent yeast; curves 2 and 3, the maximum, 

 and minimum rates of growth on 3 to 12 per ceiit yeast, and 

 curves 7, and 9, the slow growth on 2 and 1 per cent yeast. 



THE JOURXAL OF EXPERIMENT .4L ZOOLOGY, VOL. 28, NO. 1 



