Apkil 28, 1916] 



SCIENCE 



615 



the free ammonia was converted into am- 

 monium chloride, an involatile salt at the 

 ordinary temperature. The manure was left in 

 a slightly acid state so that all the ammonia 

 formed during the course of the experiments 

 would immediately unite with the acid. It 

 was tested with litmus paper for acidity be- 

 fore and after each experiment. 



Porcelain evaporating dishes 120 mm. in 

 diameter and 35 mm. deep were used as con- 

 tainers for the manure. Each was filled level 

 full. The ammonium carbonate, when used, 

 was imbedded in the manure; 57 grams was 

 the amount generally employed. Ammonium 

 hydroxide was not entirely satisfactory, be- 

 cause the ammonia escaped rapidly, and the 

 addition of a liquid to the manure made it too 

 wet. The controls held acidulated manure 

 only, and were placed two, twenty-five, thirty 

 or fifty feet from the acidulated manure which 

 contained ammonium compounds. In one ex- 

 periment the ammonium carbonate was placed 

 in a glass dish to which water was added, and 

 a dish containing acidulated manure was set at 

 a distance of one foot on each side of it. 



A summary of six experiments is given be- 

 low. Each dish with its contents is spoken of 

 as a lot: 



Total egg-masses in 10 lots of HCl manure 

 evolving ammonia from ammonium car- 

 bonate 164.0 



Average per lot 16.4 



Total egg-masses in 4 lots of HCl manure 

 evolving ammonia from ammonium hy- 

 droxide 14.0 



Average per lot 3.5 



Total egg-masses in 10 lots of HCl manure 

 separated 1-2 feet from ammoniated lots. 37.0 



Average per lot 3.7 



Total egg-masses in 10 lots of HCl manure 

 separated 25, 30 and 50 feet from am- 

 moniated lots 8.0 



Average per lot 0.8 



The lots which volatilized ammonia from 

 ammonium carbonate were more than four 

 times as attractive as the untreated acidulated 

 lots placed near them (one to two feet), and 

 more than twenty times as attractive as the 

 acidulated lots placed some distance away (25 

 to 50 feet). In the single experiment in which 



an acidulated manure lot stood on each side of 

 a dish containing ammonium carbonate and 

 water, twelve egg-masses were deposited upon 

 the acidulated manure, while none was found 

 in the acidulated manure controls thirty feet 

 distant. The oviposition response of the house 

 fly in these experiments was roughly in an in- 

 verse ratio to the distance from the source of 

 the ammonia. 



Oviposition in Timothy Chaff and Pine Saw- 

 dust. — This series of experiments was con- 

 ducted in the same manner as the acidulated 

 manure series. The chaff and sawdust were 

 always kept moist with water. The results are 

 set forth in the following table: 



Timothy chaff which volatilized ammonia 

 incited flies to oviposit on it within a short 

 time. The average number of egg-masses per 

 lot for the two experiments was 5.5, consider- 

 ably lower than the average for the acidulated 

 manure experiments. Larvae were able to de- 

 velop into normal flies in timothy chaff. 



Pine sawdust was even less attractive than 

 timothy chaff, with an average of 1.5 egg- 

 masses per lot. Larvse died soon after hatch- 

 ing in this substance. 



Oviposition in Cotton and Filter Paper. — 

 Pieces of ammonium carbonate were placed in 

 evaporating dishes, covered with sterilized ab- 



