50 
discover some easy and practical method of obtaining an extract of 
pyrethrum, which really added some insectieidal property to the remedy 
with which it was combined. For this reason in the oil experiments it 
was manifestly necessary to eliminate the factor of direct sunlight. 
In order, however, that this series might be complete in itself a few 
experiments with cold and hot water decoctions of pyrethrum were 
repeated. Their results are presented in experiments 19 to 24, inclu- 
sive. Comparing these with check experiments 25 and 26 it becomes 
evident that neither cold nor hot aqueous extracts have any value as 
remedies against the more mature larvae, and have but slight utility 
even against the youuger worms. This agrees with what has already 
been reported in Bulletin 24, p. 43. Eesults to be of great value in 
making comparative tests of the remedies should on the whole be ob- 
tained by experimenting with older individuals. In the experiments 
not already discussed considerable selection was exercised in this re- 
spect. 
The aqueous decoctions of the powder having proven of no value 
against the more mature larvae, we should expect to find that the re- 
sults of these experiments with the oil emulsions combined with these 
aqueous decoctions would not differ materially from those of the sim- 
ple oil emulsions of equal strengths. Inspecting Table XVI it is found 
that experiments 1 to 4, inclusive, were with simple oil emulsions; those 
of experiments 5 to 12, inclusive, were the same combined with cold and hot 
decoctions of pyrethrum. In Table XV equal strengths have been tabu- 
lated. Noting in this table the experiments just referred to, no appre- 
ciable difference is found in comparing experiments 1 with 5, 2 with 
0, 8, or 11, 3 with 9 or 12. For a series of independent trials the vari- 
ation in results is but slight, and the combinations in question seem, 
therefore, to have no special advantage over the simple emulsion. 
Studying next the cold oil-extract emulsions by comjjaring experi- 
ment 15 with 3, 9, or 12, which latter are simple oil emulsions of equal 
strengths, some difference favorable to the oil extract is shown. The 
difference can not be fully discussed, since, by an accident, the records 
of two of the experiments are not complete. It was observed, however, 
that the activity of the larvae treated with the oil-extract emulsion was 
more excited and pronounced than that of those treated with the sim- 
ple emulsions. 
Coming now to the hot oil-extract emulsions, we find some remarka- 
ble results. For example, in experiment 16, where a 4£ per cent dilu- 
tion of this emulsion was used, it is found that grown larvae were affected 
to an extent almost equal to a 13 per cent solution of the simple emul- 
sion. Again, in experiments It) and 17, Table XV, it is found that when 
13 per cent solutions of the hot and cold oil extracts were applied to 
grown larvae, results favorable to the emulsified hot oil extract followed, 
the latter killing every larva used in the experiment. The hot oil ex- 
tract having greatly increased the efficacy of the emulsion, it is to be 
expected that the cold oil will add to itself, in a less degree and more 
