66 J. PERCY BAUMBERGER 



other 65 per cent are sterile and can be reared on nutrient gelatin 

 in the presence of a bacterium capable of its liquefaction. These 

 larvae seldom result in normal-sized adults and it was not pos- 

 sible to raise' sterile larvae on a synthetic medium of meat ash, 

 peptone, and meat extract, acid or alkaline. Therefore Bog- 

 danow concluded: 



1. Im einfach sterilisierten Fleisclie wachst die Calliphoralarvo ge- 

 wohnlich sehr schlecht. 



2. In sterilisierten Resten der Larvennahrung wachst sie nicht besser. 



3. Ftir die gute Larvenentwicklung sind meistens gelatine verfltissi- 

 gende Bakterien oder Trypsin notig (p. 193). » 



As nutrient gelatin is a 'highly inadequate diet for Drosophila, 

 it is probable that the Calhphora reared on this medium obtained 

 some of their food requirements by digesting the cells of the gel- 

 atin-hquefying bacteria which are unavoidably ingested by the 

 larvae. As the flies were all undersized, it appears that this mi- 

 croorganism is at least not a complete food for the insect (as 

 yeast is in the case of Drosophila). Therefore, Bogdanow's con- 

 clusion, that bacteria play merely the part of liquefiers in the ecol- 

 ogy of the larvae, is largely warranted. 



Wollman ('11) repeated Bogdanow's experiments and came to 

 the conclusion that sterile Calliphora vomitora larvae can be re- 

 reared on sterile meat which has been sterilized by Tyndalizing 

 rather than autoclaving. Bogdanow had autoclaved the meat 

 used in his experunents, thus coagulating the proteins and mak- 

 ing them insoluble to the larvae which when small have (according 

 to Wolhnan) low proteolytic power. Though Wolhnan found 

 that the larvae grew more successfully in the absence of micro- 

 organisms, as putrefactive bacteria always occur in the habitat 

 of the fly, it is quite likely that they have some food value for the 

 insect. Nevertheless, Calliphora, unlike Drosophila or Lu cilia, 

 grows best in the absence of all microorganisms. 



ODORS ATTRACTIVE TO INSECTS 



The odors which are attractive to dipterous adults are usually 

 fermentation or decomposition products of the activity of micro- 



