616 



SCIENCE 



[N". S. Vol. XLHl. No. 1113 



sorbent cotton, moistened with water, and ex- 

 posed in a locality where flies were fairly- 

 abundant. Some of the dishes contained in 

 addition small amounts of the following : ethyl 

 alcoholic solution of skatol, ethyl alcoholic solu- 

 tion of indol, ethyl alcohol, phenol, valerianic 

 acid, and butyric acid. In other dishes the am- 

 monium carbonate was omitted, and the follow- 

 ing compounds were added to the moistened 

 cotton: ammonium sulphide solution, valeri- 

 anic acid, and butyric acid. There were also 

 controls of moistened cotton only. 



For the filter paper experiments, the paper 

 was torn into bits, moistened with water and 

 placed over the ammonium carbonate. In one 

 series the filter paper was stained with aqueous 

 Bismarck brown. 



Eleven experiments involving fifty-three in- 

 dividual lots" showed positive results with only 

 three combinations. These results are sum- 

 marized below: 



57 gm. ammonium carbon- 

 ate -|- 2-5 c.c. valerianic 

 acid -{- 50 c.c. water + 

 cotton 



57 gm. ammonium carbon- 

 ate -|- 2-5 c.c. butyric 

 acid -|- 50 c.c. water -\- 

 cotton 



57 gm. ammonium carbon- 

 ate -|- 20-50 c. c. water -|- 

 cotton 



Number 

 ol Experi- 

 mental 

 Dishes 



3-72 hrs. 



3-72 hrs. 

 3-72 hrs. 



Butyric acid, and to some extent, valerianic 

 acid augmented the oviposition response of the 

 house fly when added to moist ammoniated 

 cotton. Ammonium carbonate and moist cot- 

 ton without the aid of these acids brought 

 forth almost no response. 



Discussion 

 The small amount of oviposition in the dis- 

 tantly removed controls of the acidulated 

 manure series was probably due to the fact that 

 the flies were coaxed into the vicinity by the 

 odor of ammonia from the ammoniated lots 

 and came by chance to the distantly removed 



lots. These experiments show that many flies 

 went a short distance from the exact source of 

 the ammonia in order to place their eggs in a 

 favorable substance and it is reasonable to ex- 

 pect a few would stray even farther. Of 

 course a chemical substance present in the 

 manure, but not tried in these experiments, 

 may have been responsible for this slight at- 

 traction, or it may be true that an attractive 

 odor is not always necessary to induce ovi- 

 position. 



Female house flies have some power which 

 enables them to discriminate between sub- 

 stances with high food value for their larvse 

 and substances which have little or no food 

 value. This power is not infallible. Even 

 when volatilizing ammonia, pine sawdust, cot- 

 ton, or filter paper had little attraction, while 

 acidulated horse manure and timothy chafE 

 showed considerable attraction. It is sug- 

 gested that this food-discriminating power is 

 either a gustatory or a " contact-odor " per- 

 ception. 



Butyric and valerianic acids are found in 

 barnyard manure, and it seems probable that 

 their addition to ammoniated cotton gives to 

 that substance an odor which simulates to a 

 degree the odor arising from manure. If this 

 is true it explains why house flies are readily 

 attracted to ammoniated cotton to which these 

 acids have been added. It is interesting to note 

 that butyric and valerianic acids, when added 

 in small amounts to ethyl alcohol, increased the 

 attraction of the alcohol to Drosophila ampe- 

 lophila? 



I hope to give these questions further atten- 

 tion. These studies emphasize the necessity 

 for the proper disposal of all fermenting or- 

 ganic substances which volatilize ammonia, 

 and reveal possible new angles of attack in the 

 control of the house fly. 



0. H. ElCHARDSON 



N. J. Agricultural College 

 Experiment Station, 

 New Brunswick, N. J. 



5 Barrows, "William Morton, ' ' The Reactions of 

 the Pomace Fly, Drosophila ampelophila Loew. to 

 Odorous Substances," Jour. Exper. Zool, Vol. 4, 

 pp. 515-537 (5 figs.). 



