46 J. PERCY BAUMBERGER 



serve as food for the insect. Furthermore, the lar\\ae are never 

 found in any materials that are not infected with microorganisms 

 and are in a process of decomposition or fermentation, and it is 

 doubtful that the larvae find in these sul:>strata nutritional sub- 

 stances which will be of great value to them, for the food mate- 

 rials are rapidly changed to decomposition products which are 

 either absorbed by microorganisms or are too simple in composi- 

 tion to be available for the insect.-'' The real function of the 

 microorganism is to synthesize protein from ammonia, urates, 

 etc. Female flies seldom deposit eggs in substances which do not 

 have the odor of ammonia, which as products of the action of 

 yeasts, molds, and bacteria indicate the presence of the fungous 

 foods of the larvae. 



An attempt was made to sterilize Musca domestica pupae by 

 washing in 85 per cent alcohol or in 85 per cent alcohol saturated 

 with HgCU for periods of from five to forty minutes, but in each 

 of the 200 pupae used in the experiment, Aspergillus or Penicil- 

 lium mold developed around the pupa. It would seem that the 

 molds are carried within the pupae, although this is not definitely 

 proved. In this connection the following quotation from Bogda- 

 now ('08 b, p. 199) is of interest: 



Wenn Calliphoralarven bei Aiiwesenheit von Baktcrien nur von 

 Al])umosenlosung crnahrt werden konnen, so konnen die Larven von 

 Musca domestica umgekehit mit Starkckleister oder niit Gelatine ohne 

 Zusatz anderer Stoffe geftittert werden, aber, soviel ich beobachtet habe, 

 nur dann, wenn Schimmelpilze und Baktcrien da sind. 



Prowazek ('04) has found that Apiculatus fungi are usually 

 present in the intestine of Musca and Sarcophaga larvae. A 

 number of experiments have been performed to determine whether 

 or not the pathogenic bacteria, with which housefly larvae be- 

 come contaminated in their natural habitat, sui"vive in the fly 

 during the pupal period. Most of the results (Graham-Smith, 

 '13) show that only such spore-forming bacteria as anthrax pass 

 through the pupa alive. Tebbutt ('13) in this connection raised 

 houseflies on agar, a little human blood, and living bacillus dysen- 



2" Sec page 48. 



