A NUTRITIONAL STUDY OF INSECTS 



9 



However, a loose symbiosis exists between yeast and the insect. 

 As mentioned above, surface fungous growths disappear in the 

 presence of larvae which often seemed to be more numerous at 

 this point. From these observations I inferred that the larvae 

 fed upon the microorganisms present. 



g. Sterilization of pupae. The sterilization was accomplished 

 by the use of ethyl alcohol. As ^ precaution the operator's hands 

 were washed in alcohol, and a lighted burner, clean forceps and 

 platinum loop as well as sterile culture tubes were ready on a 



TABLE 1 



1 d indicates larval death 

 p indicates pupation 



table also washed with alcohol. Pupae were taken from a tube 

 having a strong growth of yeast, but uncontaminated by molds^ 

 and placed in a sterile watch-glass. Alcohol was then poured in 

 till the pupae were submerged. All floating pupae and all larvae 

 were removed. The results of this treatment for different periods 

 of time are shown in table 1. 



The pupae are able -to withstand a treatment of 25 minutes in 

 85 per cent alcohol if apphed when they are about two days old. 



^ The frequency with which pure yeast growths occur in Drosophila cultures 

 has already been mentioned on page 4. 



