February, '17] 



RICHARDSON: HOUSE-FLY FOODS 



105 



that the common carbohydrates in freshly prepared aqueous solution 

 are not eagerly sought by house-flies. 



Experiments with Alcohols and Acids 



Foods containing large amounts of fermentable carbohydrates 

 decompose with the formation of an extensive series of compounds, 

 prominent of which are ethjd alcohol, carbon dioxide, acetic acid, 

 lactic acid, a mixture of amyl and other higher alcohols called fusel 

 oil and succinic acid. Of these ethyl alcohol, technical amylic alcohol 

 (which contained a mixture of isoamyl and d-amyl alcohols, the former 

 predominating) and acetic acid were used in six experiments and lactic 

 and succinic acids in two experiments. Concentrations of 4 and 10 

 per cent were used for each compound except succinic acid. The 

 results of these experiments follow: 



Experiments on Alcohols and Acids 



Four per cent ethyl alcohol caught 891 flies; 10 per cent 544 flies; 

 4 per cent amylic alcohol was considerably more attractive, catching 

 1,256 flies, while 10 per cent amylic alcohol caught 1,119 flies; 4 per 

 cent acetic acid caught 452 flies, 10 per cent 1,242 flies, or nearly as 

 many as the 4 per cent amylic alcohol. However, a comparison of the 

 individual experiments shows that amylic alcohol gave more con- 

 sistent results than acetic acid. Four per cent amylic alcohol was 

 more than twice as attractive as 10 per cent acetic acid in four experi- 

 ments while the acetic acid was more attractive, though not twice so, 

 in two experiments. The results with lactic and succinic acids showed 

 some attraction in two experiments.^ 



^ Experiments made by Barrows (1907) on Drosophila ampelophila Loew. (Journ. 

 Expt. Zool., Vol. IV, No. 4, pp. 515-537) showed that this insect responded positively 

 to amyl alcohol, ethyl alcohol, acetic acid and lactic acid, but that the most pro- 

 nounced response was to a solution containing 2| per cent ethyl alcohol and 5/8 per 

 cent acetic acid. 



