402 KEPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



partaking are always followed by others which go through the same 

 operation. A new mode of using it was earnestly advocated and 

 strongly recommended by one of our correspondents in Texas, viz, by 

 sprinkling it, mixed in the ordinary way with from 20 to 30 parts of 

 flour, upon the ground. The locusts were found to be attracted by the 

 whitish powder, and to gather about and feed upon it. We had it 

 thoroughly tried with varying success, as the following experience indi- 

 cates : 



I have tried the experiment of Paris green and flour (1 part to 30), and do not find 

 it a success. The young locusts did not seem especially attracted to it, i. e., only from 

 a distance of a few inches, and of those which went onto it, but few died. Mr. Payne 

 states the same thing. I urged him to send a full statement of his experiment to you 

 as I knew he would have an earlier and better opportunity to try it than I should. — [A. 

 Whitman. 



In experimenting with Paris green brought in contact with the insect, I captured 

 several specimens and rubbed them in this compound, then set them at liberty 

 and watched their movements for half an hour or more. In each case I saw the insect 

 free itself by rubbing from the dry powder, and at the end of the time specified I saw 

 no difference between insects so treated and their companions. I put one specimen, 

 after thorough immersion and rubbing in Paris green, in a specimen-box, and opened 

 the box two hours after. The insect was as lively as ever, and had freed itself, as far 

 as I could see, from all traces of the chemical. Indeed, it is difficult, speaking from a 

 chemical or physiological stand-point, to see why Paris green in dry powder should 

 have any toxic effect when externally applied. Its poisonous effects are due to the 

 copper and arsenic compound of which it consists, and which can only act as a poison 

 when taken into the system in solution. 



I made the following experiments with the same substance diffused in water : In- 

 sects were kept for some time (3 minutes) in water holding Paris green in suspension. 

 On taking them out, they waited until they were dry, then brushed off the dry powder, 

 and for half an hour (as long as I watched them), behaved in all respects like insects 

 not experimented with. The reason, apparently, is that Paris green being insoluble 

 in water under these circumstances, behaves like the dry powder ; i. e., the water evap- 

 orates, leaving the dry powder, which the insects proceed to wipe off. — [R. L. Packard. 



In accordance with your request, I experimented with the Paris-green mixture. 

 Used it on an inclosed square rod of wheat ; also a rod of grass. Inclosure surrounded 

 with boards a foot wide. One-half of each of these was treated by mixing Paris green 

 with thirty-two times its weight of flour, and placing the mixture in cones upon the 

 ground. Cones formed by taking the mixture between the thumb and two next 

 fingers and compressing it, and placing the same upon the ground on about every 9 

 inches square. On the other half, the mixture was sprinkled upon the grass and 

 wheat while it was damp with dew. The mixture was eaten by the hoppers ; where 

 it was placed in cones it was covered with the insects. Should say, that in 36 

 hours one-half the quantity had disappeared, and in 48 hours there were dead 'hoppers 

 on the ground, but not in any satisfactory quantity. — [S. B. Coe, Morristown, Minn. 



I have-experimented with the arseniate of copper, as you desired, but with no prac- 

 tical effect. I mixed with dry flour first, but could find no dead locusts. I then mixed 

 into a stiff dough and worked it into crumbs or pellets, and placed on the ground, made 

 white by the dry preparation ; result, one dead sparrow, and one cowbird, both great 

 destroyers of the 'hoppers; but I could not find any dead 'hoppers, perhaps the birds 

 ate them, but I am inclined to believe that their death came by eating the poisoned 

 dough. I do not think the 'hoppers are attracted by white substances in any marked 

 degree, for on spreading the brightest rye-straw alongside of old, rotten hay, that was 

 very dark in color, I found them more numerous on the hay than on the straw. I have 





