A NUTRITIONAL STUDY OF INSECTS 41 



short period, as would have to be assumed in the case of the female 

 Drosophila. 



Guyenot ('17) has suixaned up all this work in a thesis and has 

 added some experiments concerning the exact constituents nec- 

 essary for a sjnthetic diet for Drosophila. In this he is success- 

 ful to the extent that with one exception the components of an 

 adequate diet are discovered. These are peptone, lecithin, inor- 

 ganic salts, water, and an extract of yeast, the composition of 

 which is unknown but appears to be a part of the yeast protein 

 molecule. This extracted substance is most completely removed 

 from yeast by boiling in 60 to 70 per cent alcohol and can be rec- 

 ognized by its solubility in boiling absolute alcohol, cold 70 per 

 cent alcohol, and boiling and cold water. Attempts to substi- 

 tute amino-acids, cleavage products of nucleoprotein, nuclein, 

 carbohydrates, salts, organic acids, and fats for this special sub- 

 stance were all failures. Experiments with peptone gave best 

 results when 4 per cent was used, but no larvae pupated unless 

 lecithin was added, which permitted the storage of fats and 

 pupation, but not the emergence of adults. The addition of 

 bouillon to peptone also permitted a few abnormal pupae to be 

 formed, but no adults emerged. Completely filtered autolyzed 

 yeast, together with lecithin and peptone, made a complete and 

 normal food for the insect. Liver autolyzed or extracted could 

 be substituted for the yeast extract with equal success. The 

 author also studied the formation of reserve fats and found that 

 this process depended mainly on lecithin, but could go on to a 

 slight extent at the expense of the protein derivatives in the 

 yeast extract. 



These results of Guyenot do not necessarily conflict with my 

 own, as the special substance extracted by boiling alcohol is 

 probably included in the nucleoprotein used in my experunent,^^ 

 as Guyenot has pointed out. No fats were present in the yeast 

 nucleoprotein used in my work, as I had extracted these with 

 ether. As Guyenot found that lecithin is required, there would 

 appear to be conflicting results in this regard, however, he also 



1^ In drying, the nucleoprotein was washed with cold alcohol, but the special 

 substance of Guyenot is not extracted unless the alcohol is boiling. 



