33 
periments is, that in many cases where I had applied a dilution of a given strength 
to larve of different age, the younger larvze seemed less affected than the older. 
Concerning the difference between au aqueous extract of pyrethrum made into an 
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 different. As far as their use is concerned these two 
are absolutely one. If there is any practical difference between them, the aqueous 
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 be combined in an emulsion which would be more 
effective than either. When I was assured by Mr. Mally (an agent of the Division) 
that he had made sucha 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 is 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 had tried the kerosene-pyrethrum combination according 
to Menke’s formula, but had found it of no use against the Rose Chafer. 
_In response toa question by Mr. Smith, Mr. Alwood stated that he 
buys imported powder for from 38 to 40 cents per 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 thathe 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 that 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 Cabbage Bug. Kerosene emulsion is also 
ineffective against the same insect. 
‘Mr. Alwood, however, had found it effective for this insect. 
Mr. Weed stated that he had killed the plants, but notthe 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 be caught upon Mustard before 
the cabbages are set out. | 3 
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 _. 
