EFFECT OF X-RAYS ON TRIBOLIUM CONFUSUM 579 



Experiment 5. To show that the beetles ivere not killed by ionized air 

 rather than by X-rays. 



25 beetles were carefully shielded from X-rays. Ionized aii", to- 

 gether with what little ozone and NO2 might be present was drawn 



MAM 



past the beetles dm-ing an exposure of 19,600 ^ at 50 KV. Even 



if onl}' 10 per cent of the ions remained uncombined when they reached 

 the beetles, still this would be equal to that caused directly by 1960 



^.„ at 50 KV. This dose of X-rays, acting directly on the beetles, 

 25^ 

 would have killed them all in less than 2 weeks if death were produced 

 by ionized air rather than by X-rays directly. But at the end of 21 

 days, only 1 beetle was dead. 



Therefore, the beetles are not killed by ionized air. 

 Experiment 6. To show that the beetles were not killed by too high 

 humidity rather than by X-rays. 



A. 10 beetles were put, without food, in a fiat-bottomed test tube 

 f inch in diameter, which was kept dry by a side tube filled with 

 P2O5. All but one were alive after 6 days. 



B. 60 beetles were gathered in such a way that each beetle was 

 slightly moistened on the back. They were all put, without food, in 

 a test tube, 1 inch in diameter. As they crawled over each other, the 

 moisture was spread over their whole bodies. In 6 hours most of the 

 beetles were dead. Those alive were so weak that they could not turn 

 over, even when lying on their sides. 60 other beetles gathered in the 

 same way, and put in a similar test tube, with a cloth bottom, lived. 

 The cloth bottom could only have acted as a ventilator and an ab- 

 sorber of water. 



C. Beetles are grown in an almost water-saturated atmosphere in 

 the brooders and seem to thrive well. 



Therefore, the beetles are not harmed by either extreme dryness or 

 by high hmnidit}^, but may be killed by strangulation when water is 

 condensed on them. 



Experiment 7. To find effect of X-rays on the food of the beetles. 



A box similar to those used in the preliminary experiments was 

 filled with corn meal and X-rayed 15,000 milliampere-minutes at 25 

 cm. distance at 50 kilovolts. 25 beetles were then put in this box 

 with the cornmeal. They lived lives of normal length. But beetles 

 rayed this amount die almost instantly. 



Therefore, X-raying the boxes and the food has no effect upon the 

 length of life of the beetles. 



In the light of the above experiments, it seems safe to conclude 

 that the death of the beetles recorded below was due to X-rays, 

 rather than to some accidental circumstance. 



