RELATIONSHIP BETWEEN A RED TORULA AND A MOLD. 159 



ordinarily engorge themselves with happy results, also produced 

 a rather tough mass, but not nearly as hard and tough as the 

 combination of the mold and the red toruhc. In cross sections 

 of the gut of flies which had been allowed to feed first on torula 

 and then on mold, and had then died, the gut appears somewhat 

 distended with a matted mass of mold hyphac and torula cells. 

 It seems improbable that the fly could have taken in through the 

 proboscis such large filaments, and it is believed that they must 

 have germinated and grown in the gut after the ingestion of 

 spores, or smaller portions of filament. Sections show that the 

 mold hyphse penetrate into the walls of the gut, either between 

 the cells or into them. 



This suggests that the matted mass of torula cells may be 

 firmly bound to the intestinal wall by these adhesions of mold 

 hyphse. This would, it seems, add to the blocking effect. 

 Further, the invasion of the intestinal wall might paralyze this 

 organ so that elimination could not proceed normally on this 

 account. A similar phenomenon has been described by Vincens 

 (7) in the case of bees experimentally infected with a type of 

 Aspergillus. 



That this may not be the only means by which the mold kills 

 the flies, however, was shown by placing bacteriologically sterile 

 flies on mold cultures. In preparing the flies for this purpose a 

 number of young pupae were disloged from their moorings in 

 one of the stock fly culture bottles and soaked for one minute 

 in an aqueous solution of alcohol and mercuric chloride. They 

 were then washed three times in sterile distilled water and placed, 

 with a sterile loop, upon agar and kept three days at 37 C. and 

 subsequently at about 22 C. After the adults emerged the 

 vessels containing them and the agar were returned to the 

 incubator for 48 hours and then removed. This was done to 

 detect the presence of any bacteria which might have been inside 

 the pupa cases and escaped the disinfectant. Most of the flies 

 were found to be still contaminated, but some were not, and 

 these were selected for use. The sterile flies were placed in a 

 bottle containing a pure culture of the mold and in five days all 

 were dead. 



This rapid death pointed to either an effect of the mold, or 

 starvation, or death due to drought, or all three. 



