EXPERIMENT STATION BULLETINS. ' 581 



In discussing the influence of gasoline and kerosene vapors on the 

 respiratory quotient of insects (see Table V.) it was shown by esti- 

 mations that the percentage of vapor of these insecticides was lowered 

 during the time they were left with the insects. By the same method 

 of estimation described there (HoS O4 pipette, etc.) it was proven in this 

 connection that the gain in volume of "air transferred" to insects that 

 were saturated with air-gasoline vapor was due to gasoline vapor given 

 off — i. e., the gain in volume and the amount of gasoline vapor found 

 in the ''transferred air" afterward were equal. When carbon dioxide 

 was used, its amount in the "transferred air" afterward could be found 

 by estimation also. The odor of carbon disulphide, or of nicotine could 

 be easily detected in "transferred air" when the vapor of either had 

 been previously placed with insects. 



Drv, clean insect chitin of Passalus corniitiis was tried. It would 

 take up these gases and give them off again in pure air, but the amount 

 that it could take up per unit weight was only about one-third that 

 taken up by living insects. 



The proof would seem to be complete, therefore, that living insect 

 tissues may take up the gases or vapors named very rapidly and give 

 them off again to pure air or to other gases; except as was specified 

 for oxygen, ammonia, sulphur dioxide and hydrocyanic acid gas. In 

 general, the greater the difference between the tension of any gas in the 

 air above its tension in the insect tissues, the larger was the amount of 

 the gas that became absorbed and vise versa. For example, if a group 

 of insects were kept in puire carbon dioxide for about two hours (until 

 no nitrogen was left in the tissues) and then suddenly pure nitrogen 

 was transferred to them, the amount of nitrogen absorbed was greater 

 than if it were transferred to insects that had been kept in air. 



But not all gases were equally soluble — if that expression may be 

 used — in the insect tissues. Nitrogen was taken up in the least amounts 

 of any of the gases tried. Experiment No. 7 of table VIII shows a 

 slight increase in the volume when nitrogen was transferred to insects 

 that had been kept in air. Seemingly, a decrease was to be expected, 

 if nitrogen were absorbed; but an actual increase was brought about 

 because the carbon dioxide given out of the bodies of these insects, in 

 the ten minute interval, was greater than the nitrogen taken up. In this 

 particular experiment (No. 7) 0.2 c. c. of carbon dioxide had been given 

 off and 0.15 c. c. of nitrogen had actually been taken up by the insects. 

 (These insects had been respiring normally in air just previous to the 

 nitrogen transfer.) 



Experiments were made at transferring pure oxygen to insects after 

 they had been in pure carbon dioxide, and vise versa. Also, respiration 

 experiments with insects in air and in pure oxygen were compared. Note 

 that in experiment No. 14 there was a gain of 1.5 c. c. in a measured 

 amount of oxygen transferred to insects which had been in pure car- 

 bon dioxide, showing that the carbon dioxide given off was greater than 

 the volume of oxygen taken up. Estimation showed that 1.2 c. c. of 

 oxygen had been taken up while 2.7 c. c. of carbon dioxide had been 

 given off. Thus all the experiments in this connection went to show that, 

 for a quick interval, carbon dioxide was more soluble in the insect 

 tissues than oxygen. However, oxygen would continue to be taken up 

 when present in the least amount at all and, as has already been stated, 



