68 J. PERCY BAUMBERGER 



As both Drosophila and Musca domestica feed on microorgan- 

 isms, it is of peculiar interest that the odors which stmiulate ovi- 

 position by the female are identical to those formed by micro- 

 organisms in the substratmn in which the insect nomially breeds. 

 The response of the female fruit fly to the odors of alcohol and 

 acetic acid would indicate an instinctive response to the conditions 

 best adapted to larval life, i.e., active fermentation. In the same 

 way the response of the female housefly would indicate that the 

 best conditions for housefly larvae require the presence of proteo- 

 lytic (hence odors of ammonia, etc.) and fermentative (hence 

 odor of alcohol and acetic acid) microorganisms. Richardson's 

 results therefore give circumstantial support to my conclusion 

 that the larvae of Musca domestica hve on microorganisms. 



Response to the odor of microorganisms is highly developed in 

 the larvae of the yellow-fever mosquito, Stegomyia fasciata, as 

 Bacot ('17) has recently shown that the eggs of this insect will re- 

 main for several months unhatched with the fully developed larva 

 inside if the bacterial content of the surrounding water is low. 

 The addition of foul contaminated fluid causes hatching in ten 

 minutes. It is true that a fall of 6 to 10°F. causes some larvae 

 to emerge, but the percentage is very low. Eggs were sterilized 

 and transferred to sterile fluid, but if living yeast or bacteria were 

 added they hatched immediately. Sterile autolized extract of 

 brewer's yeast had the same effect, but killed bacterial cultures 

 or watery extracts of yeast were ineffective. Bacillus coli was 

 always effective when alive. The acidity and alkahnity of the 

 different solutions were controlled. The author attributed the 

 phenomena to the sense of smell of the larva and gave an exhibi- 

 tion of larvae feeding on stained bacteria (p. 178). 



A rapid succession of different fungi occurs on manure (Gloyer 

 and Fulton, '16, p. 6) and on other decaying substances together 

 with an accompanying variety of odorous by-products. This 

 succession determines the regular order in which decaying animal 

 bodies become infested with insect scavengers. Megnin ('85) 

 and Hough ('97) have found that the order in which insects at- 

 tack a decaying body is so constant that they have been able to 

 develop a table giving the sequence of the different species. Thus 



