570 STATE BOARD OF AGRICULTURE. 



In tliese experiments, the respiratoiy quotients of the insects, after 

 treatment with carbon disulphide vapor, averaged about 0.08 higher 

 than those made for the insects in air; after treatment with To-bak-ine 

 vapor the quotients averaged only about 0.01 higher. 



In any case the insects most deeply affected by either of the insecti- 

 cides, but yet not killed at the beginning, gave the highest respiratory 

 quotients. 



It will be seen from the table that the rate of the respiratory exchange 

 was greatly lowered if specimens were deeply under the influence of 

 carbon disulphide vapor. If they were only partially paralyzed by this 

 vapor, however, the rate of the respiratory exchange might run as high 

 or higher than in air (see No, 4.). Very little carbon disulphide vapor 

 was required to render the insects helpless. On the other hand, beetles 

 were not so easily rendered helpless by To-bak-ine; and when partially 

 paralyzed, the rate of the respiratory exchange was lowered. 



If foimd during a period of decided recovery from either of these 

 insecticides, the respiratory quotient was never higher, but usually 

 just a little lower than the normal for the same beetles in air. 



CO 

 EFFECT OF AMMONIA GAS ON ^ ' OF PASSALUS CORNUTUS. 



In a preliminary study of the influence of ammonia gas upon the 

 respiratory exchange of* P. cormitus, it was soon found that, in the 

 presence of enough of the gas to noticeably inflnience the action of 

 the beetle, practically no carbon dioxide was given off; oxygen, 

 liowever, was still taken up. Furthermore, it was learned that during 

 the time beetles were confined with a certain volume of air-ammonia 

 mixture, the percentage of ammonia gas kept decreasing provided the 

 beetles remained alive) until finally no more was present in the air con- 

 fined with them. Then, almost immediately as it seemed, carbon diox- 

 ide began to appear in the respired air. 



It seemed as if the ammonia might be uniting with carbon dioxide 

 produced by the insects and that the union, perhaps, was taking place 

 within their bodies, since no solid compound formed by the two gases 

 was to be seen on the mercury or on the sides of the container. If 

 this surmise were true, it was evident that no tru^e relation could be 

 obtained between the carbon dioxide produced and the oxygen used 

 under the influence of ammonia, unless the carbon dioxide fixed in 

 this way could be liberated and estimated. 



As is well known, ammonia and carbon dioxide will unite, in a water 

 solution, to form ammonium bicarbonate. It seemed probable that the 

 conditions within the insect body might be favorable for such a com- 

 bination. 



Now if ammonium bicarbonate is boiled in a water solution, it be- 

 comes broken up — the products, ammonia and carbon dioxide, both 

 being driven off. This test was therefore tried with insects. Beetles 

 that had been treated for several hours with ammonia were afterward 

 dropped into boiling water and distilled, when })oth ammonia and car- 

 bon dioxide did appear in the distillate. If untreated beetles were dis- 

 tilled in boiling water a small amount of carbon dioxide but no am- 

 monia was obtained. 



Finally then, the following method for making the required determi- 



