A NUTKITIONAL STUDY OF INSECTS 



19 



that some vitamine may be absent or may have been destroyed 

 by the high temperatures of the autoclave. 



Some Ught is thrown on these questions by a comparison of the 

 rates of growth of larvae on banana media which have been more 

 highly concentrated by partial desiccation or by extraction with 

 hot water. The growth of insects on these media is shown in table 

 6 and figure 5. 



On sterile food consisting of mashed whole bananas, especially 

 when they have dried out slightly and are thus concentrated, an 

 occasional small pupa is formed. On a hot aqueous extract of ba- 

 nana a larger number is formed from which small adults emerge. 



TABLE 6 



Banana n.ash 1 



Banana mash 2 



Banana mash 3 



Banana mash (slightly shrunken) 4. 

 Cold aqueous extract of fermented 



banana 

 Cold aqueous extract of unfermented 



banana 



Hot aqueous extract of unfermented 

 banana 



LARVAL PERIOD 



(20 OR MORE LARVAE IN 



EACH case) 



11 days 

 7 daj^s 



22 days 

 13 daj'^s 



28 days (Average) 



12 days (Average) 

 25 days (Average) 



13 days (Average) 

 20 days 



29 days 



9 days (Average) 



9 ^ 



+ 



+ 

 + 



+ 



These are potentially fertile, for when fed with yeast, the females 

 deposit fertile eggs from which normal larvae emerge. This will 

 be discussed below at greater length. On cold aqueous extracts 

 of unfermented banana, no larvae pupate. 



These results show that concentrated banana permits complete 

 and more rapid growth of larvae. Therefore, the fruit is not en- 

 tirely lacking in any amino-acid necessary for growth nor is any 

 vitamine absent or destroyed by steriUzation. It appears, more- 

 over, that concentrated banana forms a complete food for Dro- 

 sophila larvae, i.e., the protein deficiency of fniit is quantitative 

 rather than qualitative. 



