A NUTRITIONAL STUDY OF INSECTS 25 



the insect. As the sugars and inorganic salts are abundantly 

 present in fniit^- and the addition of nucleoprotein of yeast is 

 sufficient to make the synthetic medium a complete diet for Dro- 

 sophila, it can be said that yeast is a more adequate food than fruit 

 because of its high protein content. 



g. Conclusions. 1. Insects can be conveniently reared in a 

 solid agar medium. 



2. Larvae prevent the development of molds on the medium, 

 but are always associated with living yeasts. 



3. For genetical work fermented banana agar or Pasteur's 

 culture fluid agar is most convenient. 



4. Living yeasts are not present in the egg or pupa. 



5. The exterior of pupae can be sterilized by washing in 85 

 percent alcohol for twenty minutes. Yeast cells are more readily 

 killed by this treatment than molds. 



6. Banana agar is a good culture medium for fungi. 



7. Sterile larvae grow more slowly than non-sterile larvae on 

 sterile fruit; the rate of growth can be increased by infecting the 

 medium with living yeasts. 



8. The alcoholic treatment in sterilizing pupae is not the cause 

 of the slow growth of larvae on sterile food. 



9. The simplest nutrient medium for yeast, if infected with 

 living yeast, is equivalent to fermenting fruit in the ecology of 

 larvae. 



10. Sterile fruit has greater food value for larvae than ' 'sterile 

 nutrient medium for yeast." 



12 Atwater and Bryant ('06) give the following analysis of the edible portion of 

 banana : 



Total car- 

 Water Protein Fat bohydrate Ash Fuel value 

 per cent per cent per cent per cen t per cent per lb. 



Minimum 66.3 1.0 0.0 16.3 0.5 330 



Maximum 81.6 1.6 1.4 29.8 1.1 640 



Average 75.3 1.3- 0.6 22.0 0.8 460 



Prescott ('17) gives this analysis of banana ash: 



percent percent percent 



Silica 2.19 Phosphoric acid.. . 7.68 Potash 43.55 



Lime 1 . 82 Magnesia 6 . 45 Sulphur trioxide . . 3 . 26 



Iron oxide 0.18 Soda 15.11 Chlorine 7.23 



