12 J. PERCY BAUMBERGER 



If sterile pupae are placed on a sterile medium of banana agar 

 and protected from contamination, the adults emerge and ovi- 

 posit, but the larvae that hatch develop very slowly and finally 

 die before pupating. The great difference in rate of growth be- 

 tween sterile and non-sterile larvae on the same food is shown in 

 figure 2. In cultures A 10, 11, 12, amd 17 living yeast cells were 

 present and the larvae grew at a normal rate, reaching the full 

 length of 8 mm. in eleven to twenty-sLx days when pupation took 

 place. In cultures^ A 18 and 25, on the other hand, the sterile 

 larvae reached a size of only 3 mm. after twenty-eight to forty- 



Fig. 2 Larval growth on banana agar. A 10, 11, 12, 17, growth in cultures 

 infected with living yeasts; A 18, 24, 25, slow growth of larvae in sterile cultures; 

 A 24, infected with living yeast on twenty-sixth day, causing an increase in 

 growth. 



four days, when they died. In culture A 24 the sterile larvae 

 reached a length of 2 mm. in twenty-six days when the medium 



^ The size of the larvae on different media was determined by placing the tubes 

 and a millimeter scale on the stage of a binocular microscope and measuring the 

 length of five to ten of the larger specimens while 'crawling' at full length. The 

 larger specimens were selected for measurement because, although female adults 

 were allowed to oviposit for only one day, the eggs showed considerable variabil- 

 ity from one to three days in their date of hatching, depending on the readiness 

 with which the female oviposited on the medium. 



The cultures were kept in a steam-heated room in which the maximum tem- 

 perature for the entire period of experimentation varied between 96° and 71°F. 

 and the minimum between 73° and 56°F. As compared experiments were run 

 parallel in time, the error due to temperature differences should not be great. 



It should be kept in mind that each point on a curve of growth is the average 

 of the whole culture of larvae, i.e., usually twenty or more individuals, thus a 

 single curve has considerable weight. 



