EFFECT OF X-RAYS ON TRIBOLIUM CONFUSUM 577 



vestigating the relation between the latent-interval and the 

 X-ray dosage. This required a large number of beetles and it 

 was necessary to determine their life history and how best to 

 propagate them. It was found that they grow and propagate 

 best in oatmeal or whole-wheat flour, but they will live in corn 

 meal, white flour or any of the prepared cereal products. Prop- 

 agation takes place best at a temperature of 35 to 36°C. and at 

 high humidity. Temperatures of 45°C. or over are fatal. The 

 eggs are white and from 0.3 to 0.6 mm. in diameter. They are 

 usually associated with pieces of grain. Larvae grow to a length 

 of 5 or 6 mm. and shed their skins six times. Pupae are white. 

 Young beetles are a light straw color which later darkens to a 

 russet. The beetles are about 4 mm. long. They are especially 

 adapted to such work as is reported here because they are small, 

 harmless, easy to handle and count in large numbers; they 

 propagate readily, can not crawl out of glass beakers or small 

 porcelain crucibles, and show little tendency to fly. 



In the preliminary experiments mentioned above, the beetles 

 were packed in small wooden pill boxes with some food. There 

 were 25 beetles in each box. There was a possibility that death 

 was not due to any action of X-rays on the beetles, but might 

 have occurred from any of the following causes: 



1) Lack of air and food 



2) High temperature due to overcrowding 



3) Injury due to overcrowding 



4) NO2 caused by the high voltage connections of the X-ray 

 tube. 



5) Ionized air 



6) Excessive humidity 



7) Effect of X-rays on the food in the boxes or even on the 

 boxes alone. 



The following seven experiments were therefore done. 



Experiment 1. To show tha' the beetles were not killed by lack of air 

 and food rather than by X-rays. 



A. 10 beetles were sealed up in a glass tube with a rubber stopper, 

 without food, in a space 0.05 cubic inch. They were all alive at the 

 end of 76 hours. 



