4S0 STATE BOARD OF AGRICULTURE. 



with the beetles. After 10 mimitea the whole remaining volume was 

 returned to the compensation-burette and again accurately measured. 

 The first readinjif minus the second readinjj oip the compensation burette 

 showed the amount of vapor that had been absorbed by the insects. The 

 gas could thus be transferred back and forth at intervals to obtain ab- 

 sorption values at 10. 20 and 30 minute intervals, if desired. At the end 

 of this test in the cold room, the beetles were removed to fresh air; and 

 after an hour or two were brought into the warm room along with the 

 apparatus and the stock supply of insecticide vapor. After 18 to 41 

 hours, when the beetles had become active and everything to be used 

 had reached the room temperature, absorption-tests were again carried 

 out with the same insects — using a sample of the same insecticide vapor 

 under the new conditions. Now, gasoline did not produce a very high 

 percentage of vapor at the cold room temperature; and a tluid which 

 would give a higher percentage of vapor at the low temperature seemed 

 desirable. On that account, ether was selected for the new trials instead 

 of gasoline. 



Four experiments were carried out in the manner just outlined, using 

 P. coniutus, and the vapor of ether in air. The results of all four of 

 the experiments are given in Table VIII. In no case, as may be seen, 

 were the absorptions less than two times greater in the warm room, 

 where the beetles were active, than when the latter were dormant in the 

 cold room. In experiments 3. 4 and 5, in the cold room, the small amount 

 of absorbed ether-vapor stimulated the dormant . insects until they 

 twitched the antennae and moved the legs. On the other hand, in the 

 warm room tests of Exp. 3, the active beetles had become entirely 

 motionless (anaesthetized) in 10 minutes; at the end of Exp. 4, only a 

 bare movement of the antennae could be noticed, still ; and in the warm 

 room test of Exp. 5, the active beetles w^ere completely anaesthetized by 

 the end of 20 minutes. In the case of Exp. 6, the beetles were entirely 

 stiif and helpless at minus 2.4° C, and they remained so even under the 

 influence of the small amount of ether absorbed. When these insects 

 were removed from the lirst test, they showed no movement whatever; 

 and they recovered from the cold, only slowly, after being brought into 

 the warm room. They had been kept in the cold (at minus 2.4° C.) 

 only a few hours in all. A different stock supply of ether-vapor-air was 

 used in Exp. 6, and the five beetles absorbed only 1.5 c. c. of the vapor 

 even in the warm room in 20 minutes. This was barely enough of the 

 ether to place the insects in the excitement state — they were more active 

 at the end than at the beginning of the last test. 



In order to show how nearly constant a certain volume of pure air 

 remained during a period of 30 minutes with five beetles, a single check 

 may be related. The five beetles used weighed 10 grams. The 50 c. c. 

 of pure air was transferred from the compensation burette to the con- 

 tainer with the beetles and back again three times during the check, 

 with the following results : 



50.0 c. c. at the beginning; 



50.2 c. c. at end of 10 min. (after first transfer) ; 



50.0 c. c. at end of 20 min. (after second transfer) ; 



49.9 c. c. at end of 30 min. (after third transfer). 



The six experiments (Table VIII) were carried out with such care, 



