December, '17] crumb and lyon: house-fly and chemicals 



533 



bubbled through the Hquid in the bottle where the rate of flow is indi- 

 cated by the number of bubbles produced per minute. 



In selecting a material through which to percolate the odors to be 

 tested, it was necessary to obtain something having a texture satis- 

 factory to the ovipositing fly but which did not possess further inciting 

 qualities. After testing asbestos, absorbent cotton, abraded blotting 

 paper, ground chaff, animal charcoal, wheat bran and some other sub- 

 stances, the bran was selected as most nearly fulfilling these conditions. 

 A special grade of this material 

 was obtained which was nearly pure 

 husk. This was thoroughly washed 

 and dried in the sun and before 

 use was moistened, packed in the 

 funnels, and sterilized bj^ steam for 

 an hour or more. The use of this 

 bran did not entirely eliminate eggs 

 in the checks probably for the reason 

 that the texture of the medium 

 may be a secondary stimulant to 

 oviposition. 



Each unit of the apparatus for 

 testing carbon dioxide consists of a 

 milk bottle equipped as in the am- 

 monia apparatus (see Fig. 27) except- 

 ing that the connecting tube from 

 the compression chamber in the 

 ammonia apparatus is replaced by a 

 dripping funnel having a ground-glass 

 stopper. The bottle was charged 

 with pure carbonate in a little 

 water and the dripping funnel with 

 pure sulfuric acid diluted one to 

 four. When the apparatus was in 

 operation, the acid was allowed to 

 drip into the bottle at such a rate 

 that a continuous slow generation 

 of carbon dioxide resulted. Calcium 

 carbonate was used in the bottle 



to some extent but the sodium compound was found more satisfactory 

 and was the carbonate chiefly employed. In interpreting the results 

 of the experiments it should be borne in mind that the products of the 

 reaction between the carbonate and sulfuric acid are a sulfate and car- 

 bon dioxide and that the sulfate in both cases is non-volatile at ordi- 

 nary temperatures. 



Fig. 27. Cross section of one unit 

 of apparatus for testing the effect of 

 ammonia on house-fly oviposition: 1, 

 Cross section of water tank; 2, con- 

 necting tube between water tank and 

 compression chamber. In use the 

 spring clip was replaced by a tubing 

 clamp for regulating the rate of flow 

 of the water; 3, compression chamber; 

 4, milk bottle containing lic^uid to be 

 tested; 5, porcelain funnel bearing 

 wheat bran on the perforated por- 

 celain partition. 



