172 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



and then if the same hidividuals were doubly resistant we might have 

 to introduce a weak strain of the the San Jose scale to cross with the 

 immunes and thus return to the normal susceptible population. 



President P. J. Parrott: This is a very unique paper and ought 

 to provoke considerable discussion. 



Question : Are the records on the chart the result of a single year's 

 experiment or combined results of several years? 



Mr. a. L. Melander: The curves were built up from last year's 

 work at three different places. 



Question: Can you tell us why the Clarkston results were not as 

 good as the others? 



Mr. a. L. Melander: I tried to explain in the paper that I believed 

 that the Clarkston scales possessed a hereditary resistance to the lime- 

 sulphur spray. This may possibly be due to the fact that they have 

 been subjected to this spray longer than any other place, for the lime- 

 sulphur has been used longer in that valle}' in Washington than any- 

 where else in the northwestern part of the country. 



Mr. W. C. O'Kane: I was interested in what the speaker had to 

 say in regard to the immunity of caterpillars to arsenic. I would like 

 to know whether, after the first or second spraying, the caterpillars 

 were increasing in size, and resistance, and were consuming much more 

 than a dose which would ordinarily kill them? 



Mr. a. L. Melander: He told me that they were feeding and 

 consuming man}- times as much poison as should ordinarih^ kill them. 



President P. J. Parrott: Can Doctor Wheeler give us any figures 

 on the experiments which were conducted by Mr. Glaser? 



Mr. W. M. Wheeler: Mr. Glaser did not advise me in regard to 

 the results of these experiments. I think they were taken up in con- 

 nection with other work. 



Mr. E. p. Felt: I would like to ask Mr. Burgess if it is not a fact 

 that when the gipsy moth caterpillar becomes nearly grown it is very 

 difficult to destroy it with poison. 



Mr. a. F. Burgess: Yes, that is true. If spraying is done when 

 gipsy moth caterpillars are nearly full-grown it is very difficult to kill 

 them. I think Mr. Glaser must have secured these results in connec- 

 tion with other experiments which he was carrying on. 



President P. J. Parrott: In using the lime-sulphur wash we 

 have found from past experience that spraying may not kill the parent^ 

 although the treatment is destructive to the progeny. Has this been 

 your experience? 



Mr. a. L. Melander: Considering the results from a chemical 



