160 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



Mr. Dean: If the egg is subjected to a temperature of 120° it 

 perishes in a short time. 



Mr. Washburn: No injury to mill products? 



Mr. Dean: None. 



Mr. Lowe: Do the insects leave the flour wlien they are about to 

 die? 



Mr. Dean: I will say this, I saw a great many dead insects on the 

 floor. They became uncomfortable and rushed out into the hot 

 air. They did not get far and never reached the window and many 

 times did not go four or five inches. 



Mr. Smith : This promises to be a very beneficial and useful method, 

 and it occurs to me that in large stores which frequently have insect 

 pests, if this- method was available it would be a blessing, especially to 

 tobacco factories and the like. I should like to ask Mr. Dean if he 

 has made any experiments outside of mills, and on other insects. 



Mr. Dean: The experiment was tried only on the five mill insects 

 stated in the paper. Of course, these experiments are going to be 

 continued. 



Mr. Sanborn: I would like to ask Mr. Dean if he thinks this 

 method might not be of considerable importance in the treatment 

 of nursery stock for San Jose scale. 



Mr. Dean: I can say nothing definite on this phase of the subject, 

 but sim.ply make the assumption that I cannot believe any insect is 

 going to stand very much heat. 



Mr Shafer: I think the last statement by Mr. Dean is very 

 true. In histology one of the very best methods of fixing insects is by 

 heat. You can fix. the parts of an insect quicker by heat, perhaps, 

 than by any other method that has yet been found. If you go above 

 150° you get the tissues fixed all the way through and if you do that, 

 of course, you kill the insect. Another point, in regard to the pene- 

 tration of hydrocyanic acid gas: In the work we had to do with that 

 gas we had a little thing come up, which shows why the gas does not 

 penetrate. I took the percentage of gas in a certain amount of air 

 at the beginning of the experiment, and at the end and found the last 

 precentage of the gas very low. It would fall very rapidly, and if 

 I had 77 per cent in a half hour it might fall to 5 per cent, that is the 

 gas was reducing rapidly — the higher precentage of gas the more 

 rapidly it would fall. Now, if you had some substance like flour 

 which contains moisture, it would be taken up by that moisture, and 

 I think these tAvo reasons would account for the fact that the gas 

 does not penetrate. In the case of carbon bisulfid my experience 

 has been that it does not reduce at all, and I believe, if given time, 

 it would go through. 



