33 



poriinonts is, that in many cases where I had applied a dilution of a given strength 

 to larvio of dirtereut age, the younger laivaj scemod less aft'ected than the older. 

 Concerning the difi'eienco between an aqueous extract of pyrethrum made into au 

 emulsion with kerosene and soap, and a kerosene extract of pyrethrum made into 

 an emulsion with soap and water, there is no practical difference. It may be of 

 some slight interest to scientific people to know that the aqueous extract and the 

 kerosene extract are technically dilferent. As far as their use is concerned these two 

 are absolutely one. If there is any practical difference between them, the a([ueou8 

 extract emulsion is preferable. I have never made any public claim to having orig- 

 inated the idea that kerosene would dissolve the insecticide principle of pyrethrum. 

 What I wanted to announce the discovery of was, that the two insecticides, kero- 

 sene and pyrethrum, could bo combined in au emulsion which would be more 

 effective than either. When I was assured by Mr. Mally (au agent of the Division) 

 that he had made such a mixture while working with Mr. Gillette, my personal in- 

 terest in the matter ceased. Dr. Menke claims to have discovered an "entirely new " 

 insecticide which i3 remarkable for its cheapness. I think I have shown that it is 

 composed of the same materials which may be used in the same proportions so that 

 the difference between his emulsion and Mr. Gillette's is in method of preparation, 

 and in this respect his method is decidedly the inferior. The chief difficulty in the 

 use of pyrethrum in kerosene emulsion is the cost when compared with the cost of 

 the arsenites in the form of powder or in solution. 



Mr. Smith bad tried the keroseue-pyrethruin coiiibination according 

 to Menke's formula, but had found it of no use against the Rose Chafer. 



In response to a question by Mr. Smith, Mr. Alwood stated that he 

 buys imported powder for from 38 to 40 cents iier pound at wholesale in 

 New York. For buhach he has to pay 75 cents per pound and considers 

 that one is as good as the other. He finds that he can keep the powder 

 in bulk for two or three years, with care. 



Mr. Webster stated that he could buy it by the 10 or 20 pounds in La 

 Fayette, Ind., at 30 cents per pound. 



Mr. Alwood stated tliat in his opinion this powder must be adulter- 

 ated on account of the cost of production in Dalmatia. 



Mr. Smith buys in Philadelphia for 25 cents per pound, 



Mr. Weed had found kerosene combined with pyrethrum perfectly 

 useless against the Harlequin (^abbagc Bug. Kerosene emulsion is also 

 ineffective against the same insect. 



Mr. Alwood, however, ha<l found it effective for this insect. 



Mr. Weed stated that he had killed the plants, but not the bugs. He 

 has found the eggs of this insect to hatch in three days in Mississippi 

 (first brood), those of the second brood hatching in two days, and those 

 of the later brood in four days. These periods, however, are not definite, 

 and conside: able variation occurs. 



Mr. Smith finds this species in southern New Jersey, but never upon 

 cabbages. 



Mr. Doran stated that the bugs can bo caught upon Mustard before 

 the cabbages are set out. 



Mr. Weed said that he had experimented in that direction and recom- 

 mended the application of pure kerosene upon the first brood of bugs 

 upon Mustard. 



7911— No. 1 3 



