1916] Attraction of Dipter a to Ammonia 411 



It will be noted that the activating substances where their 

 exact chemical nature has been determined, are for the most 

 part organic compounds, some of considerable complexity. 

 Ammonia is the only one among these which is not a carbon 

 compound, and it is the simplest in molecular structure. 



THE EXPERIMENTS. 



The flies were captured in screen wire traps nine and three- 

 fourths inches high and six inches in diameter at the base. 

 Pieces of commercial ammonium carbonate were placed in 

 glass dishes in the pan of the trap and a little water was usually 

 added to each glass dish. Ten experiments involving twenty- 

 three traps, each containing from eighty-five to two hundred 

 and thirty-four grams of ammonium carbonate and seventeen 

 controls with or without water were carried out during the 

 summer. The results, excHisive of house-flies caught are given 

 in the following table : 



Table A. 



Traps containing ammonium carbonate Control traps: 

 Number Number 



caught caught 



Phorbia sp 15 



Muscina stahulans 11 



Ravinia communis 1 2 



Fannia canicularis '. . . . 1 



Lucilia sericala 1 1 



Ophyra leucosloma 2 



Stomoxys calcitrans 3 



Leptocera ferruginata 106 



Sepsis minuta 2 



An ortalid, Leptocera {Limosina) ferruginata Steub. was a 

 frequent visitor to the traps and an undetermined Phorbia and 

 Muscina stahulans Fall, were caught often enough to suspect 

 they were attracted by the odor of ammonia. Leptocera is so 

 small that it can pass through the meshes of the trap screen 

 readily and only those individuals that fell into the solution 

 were captured. Had the meshes been small enough to retain 

 the flies which entered the traps, I beheve the number would 

 have been far larger. In the oviposition experiments with the 

 house-fly, Leptocera, was almost always present, running about 

 in the dishes containing ammoniated manure, timothy chaff 

 and pine sawdust and even coming to those which held the 

 ammoniated cotton. It was an abundant species in accumula- 

 tions of horse manure at New Brunswick. Sepsis minuta Wied. 



