February, '10] GILLETTE: SULFID OF ARSENIC 29 



methods will involve an accurate knowledge of the life history of the 

 flies and of their ecology, and experiments to determine the effect of 

 the oil on fish as applied at different times and by different methods. 

 We hope to be able to carry on such investigations in the future, but 

 as such work involves considerable expense, for which we have no funds 

 definitely appropriated, the completion of the work may not be possi- 

 ble in the near future, so that it would seem well to call the attention 

 of others to the work, since they may have a chance to give it the 

 requisite study. 



Pbbsident Britton : We will now listen to a paper by Prof. C. P. 

 Gillette, Fort Collins, Col., on "A New Arsenical Poison for the Cod- 

 ling Moth." 



NEW SPRAYS FOR THE CODLING MOTH 



By C. P. Gillette, Fort Collins, Col. 



When Doctor Headden announced^ his conviction that the arsenical 

 sprays used for the control of the codling moth are, in many instances, 

 killing the apple trees, he was asked to suggest some poison that would 

 be less injurious to the trees and still give promise of killing the 

 worms. He suggested trying sulfid of arsenic (ASg S^ ), and ex- 

 pressed the fear that it would not be sufficiently soluble in the diges- 

 tive fluids of the larvse to kill them. Knowing something of the great 

 digestive powers of insects, I expressed to the doctor a very strong 

 desire to try arsenious sulfid in comparison with arsenate of lead in 

 some codling moth spraying experiments already planned for 1909. 

 Doctor Headden first prepared a small quantity in liquid form which 

 was tested upon different kinds of foliage in the insectary to determine 

 the strengths that might be safely used upon the leaves. 



It was nearly time to begin the work of spraying for the codling 

 moth, and as we could not obtain a sufficient quantity of this poison 

 near at hand for the experiment. Doctor Headden converted his experi- 

 mental laboratory into a laboratory for the manufacture of arsenious 

 sulfid.- Enough was made to use upon a few trees and was sent to 



' Bulletin 131, Colo. Agr'l Exp. Sta. 



^Doctor Headden describes Ms preparation of the poison as follows: 

 The arsenious sulfid was prepared by the usual method, i. e., -precipitation 

 by hydrogen sulfid. The washed precipitate was dissolved in lime-sulfur 

 solution, usual strength. The lime-sulfur solution was used because it dis- 

 solves, or is assumed to dissolve, the arsenious sulfid to a sulf. arsenite with- 

 out the formation of an oxygen salt, the arsenite which I wished to avoid, as 



