340 EDWARD F. ADOLPH 
Similar experiments by Evans (16) showed that the house 
fly usually lays eggs only in manure less than one day old, which 
has the highest ammonia content. He found that the larvae 
were unable to develop in neutral or acid manure—just the re- 
verse of the acid condition favorable for growth in the fruit fly. 
Howlett (15) has shown that Sarcophaga will lay its eggs 
upon scatol and that Stomoxys will lay upon valerianic acid. 
CONCLUSIONS 
1. Single stimuli do not call forth any considerable amount of 
egg-laying in the female Drosophila. When odors and textures 
are properly combined, the fly may lay nearly as many eggs as 
when natural conditions prevail. The presence of moisture char- 
acterizes all conducive complexes. The most stimulating sub- 
stances are known to occur in the natural food material of the fly. 
2. A slight amount of egg-laying takes place under the simplest 
conditions that can be presented. The only internal factor of 
importance is the attainment of ‘sexual maturity. Mating, 
nutritive condition, and internal periodicities seem to have some 
influence upon the production of eggs. 
3. The role of odorous substances as stimuli in egg-laying has 
been studied quantitatively in detail and the relative values of 
various substances as stimuli have been compared. 
BIBLIOGRAPHY 
Back, E. A., AND PEMBERTON, C. E. 1914 The life history of the melon fly. 
Jour. Agr. Res., vol. 3, pp. 269-274. 
1915 a Susceptibility of citrous fruits to the attack of the Mediter- 
ranean fruit fly. Jour. Agr. Res., vol. 3, pp. 311-330. 
1915 b Life history of the Mediterranean fruit fly from the standpoint 
of parasite introduction. Jour. Agr. Res., vol. 3, pp. 363-374. 
BaiLtey, E. M. 1906 Studies on the banana. Jour. Biol. Chem., vol. 1, pp. 
355-361. 
Barrows, W. M. 1907 The reactions of the pomace fly, Drosophila ampelo- 
phila Loew, to odorous substances. Jour. Exp. Zodl., vol. 4, pp. 515- 
587. 
BAuMBERGER, J. P. 1919 A nutritional study of insects, with special reference 
to microérganisms and their substrata. Jour. Exp. Zodél., vol. 28, 
joyo Ifoile 
BicELow, W. D., anp DunBar, P. B. 1917 The acid contents of fruits. Jour. 
Indus. Engin. Chem., vol. 9, pp. 762-764. 
