428 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



47, 49 Control 



60, 52 CO, 8-6 



61 Ammonium carbonate " 



63, 54 Control 



65, 59 Control 8-7 



66. 58 CO, 



57 Ammonium carbonate " 



Fifty-five carbon dioxide, 23 ammonium carbonate and 59 control 

 experiments were completed. Carbon dioxide gave entirely negative 

 results; the same was true of the controls. Fourteen of the ammonium 

 carbonate experiments were positive, yielding 1890 eggs, an average of 

 135 eggs for the positive experiments and 82.2 eggs for the entire 23 

 experiments. There were 62 egg masses and 26 single eggs or an average 

 of 4.4 masses and 1.9 single eggs for the successful experiments. In 

 view of the small number of flies present, oviposition in 61 percent, of 

 the ammoniimi carbonate experiments is considered significant. It is 

 believed that stormy and cool weather tended to prevent oviposition on 

 certain days. 



House-flies often crawled over and fed upon the moist bran in both 

 the carbon dioxide and control experiments. However, the preovi- 

 position behavior of backing into crevices and extruding the ovipositor, 

 so often manifested on bran containing ammonium carbonate, was 

 never observed in the carbon dioxide or control experiments. We 

 therefore conclude that the house-fly in its natural environment will 

 not oviposit on bran from which carbon dioxide alone arises. Nor will 

 it, under the conditions here set forth, oviposit in bran within 11 hours 

 after it has been moistened with water. Bran, on the other hand, 

 which evolves the final decomposition products of ammonium carbonate, 

 e.g., ammonia, carbon dioxide, and water, will attract the house-fly 

 and induce oviposition. Water is probably essential to induce ovi- 

 position; however, since water was common to all experiments it could 

 hardly have influenced the choice. Carbon dioxide itself was ineffec- 

 tive. By elimination, then, only ammonia remains and we do not possess 

 sufficient evidence to justify a revision of the former conclusion,^' ^ 

 namely, that ammonia is largely responsible for the attraction of the 

 house-fly to fermenting organic substances. The possible attractive 

 influence of carbon dioxide in mixtures of ammonia, water vapor and air 

 must be admitted, although this influence is probably an augmenting 

 rather than a determining one. The presence in the air of undissociated 

 molecules of ammonium carbonate, even in small amounts, may also 

 have an effect which was not detected. 



Ammonium hydroxide solutions were used in 36 experiments of a 

 preliminary character. Concentrations of 2, 5, 7, 10, and 14 percent, 

 ammonia were made up from ammonium hydroxide containing 28 



