INSECT POWDER. 
81 
From these results it is seen that the fruit from commercial sam- 
ples of "open" flowers contains about 90 per cent of the total nitrogen. 
Practical tests were made by E. W. Scott and W. S. Abbott, of 
the Bureau of Entomology, on roaches with the different parts of 
the finely-powdered flowers, to determine their relative insecticidal 
strength. The roaches were dipped in the powder until all parts 
of the body were covered with it, and then placed in 8-ounce bottles, 
one insect to a bottle, 10 insects being used in each test. All of the 
insects were allowed ventilation, but no food or water. The average 
of the 10 tests in each case is given in Table 49. 
Table 49. — Insecticidal strength of finely -powdered parts of insect flowers. 
Sample 
No. 
Source. 
Time 
required 
to 
paralyze. 
Time 
required 
to kill. 
Entire "open" flowers of C. cinerarisefolium 
Fruit from sample 1 
Ray flowers from sample 1 
Receptacle from sample 1 
Involucre from sample 1 
Disc flowers from "closed" flowers of C. cinerarisefolium. 
Stems 
Flowers of C. roseum 
Check 
Minutes. 
3.7 
2.4 
1,800 
90 
240 
Hours. 
21 
63 
50J 
80 
31i 
131 
23 
Apparently the fruit and disc flowers of the Chrysanthemum cine- 
rarisefolium are the parts most active in paralyzing and killing roaches. 
These are the same parts that show the highest content of nitrogen, 
so that this element, although not actually a constituent of the active 
principle, appears to be present with it in a constant ratio, and hence 
can be used as a measure of the insecticidal activity. 
Summary of work on the active principle. — All of the common organic 
solvents completely remove the insecticidal principle from the flowers 
of the C cinerarisefolium. The insecticidal principle is not re- 
moved by a steam distillation, either in neutral, acid, or alkaline 
solution. It is insoluble in water and dilute acids, but dilute potas- 
sium hydroxid solution removes nearly all of the activity from the 
powdered flowers. It is shown conclusively that the active, principle 
contains no nitrogen and is not an alkaloid. A considerable amount 
of resin is present in Pyrethrum, but this is inert when tested upon 
roaches. Alcoholic potash saponification completely destroys the in- 
secticidal activity of the petroleum-ether extract, the ester being split 
up into acids and resinous materials. The results of the work indi- 
cate that the insecticidal activity of Pyrethrum is due to a mixture of 
acids and esters. 
139815°— 20— Bull. 824 6 
