A NUTRITIONAL STUDY OF INSECTS 



31 



require sugar as food. On nucleoprotein and sugars larvae li^'e 

 ten to twenty-one dsiys, grow to full size and pupate nonnally 

 and adults live more than five days. On nucleoprotein and 

 water, however, the larvae Uve five to twent3^-one days without 

 marked increase in size, but all adults die in one to four days. 

 These results are shown in table 7 and figure 7. On plain sugar 

 and inorganic salts, adults hve five to ten days, while larvae 

 die in less than five days without increasing in size. The facts 

 are summed up in table 10. 



These results show that larvae require sugars for successful 

 pupation, but h^'e longer on pure'^ nucleoprotein than on pure 

 sugar. Adults, on the contrary, li\'e longer on pure sugar than 

 on nucleoprotein alone. 



From general observations it appears that adults oviposit 

 more readily on sugar agar than on nuleoprotein agar, but de- 

 posit most eggs and over the longest period on nucleoprotein- 

 sugar agar. Therefore it would seem that sugars stimulate ovi- 

 position and nucleoprotein increases egg production and that both 

 sugars and proteins are necessary for the normal acti\'ities of 

 both larvae and adults. 



c. The natural habitat of Drosophila. I have alread}' shown 

 by experiments that Drosophila requires sugars and protein and 

 that these substances can be supphed in a most normal form in 

 yeast cells, so that it is of interest to study the conditions that 

 exist in the natural environment of the insect. 



Schultze ('11) has recorded the fly as occurring in many dif- 

 ferent fermenting and decaying fruits, vegetables and fungi, fer- 

 menting tree sap, vinegar, tumors, and animals preser\-ed in for- 

 mol. Sturtevant ('16) describes a number of new species of 



" Carbohydrates are formed as decomposition products of nucleoprotein. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY', VOL. 28, NO. 1 



