c4 
in pain. In twenty, they were also exuding a green fluid from their 
mouths. In thirty, all were still alive, but were stupidly rolling 
about on the table,. In forty minutes, one was lfeless, and the 
others were curling up as if nearly dead. In fifty minutes, two were 
still capable of motion, but the other two were helpless or nearly 
so. In an hour, three still showed some signs of life, but were barely 
able to move. In three hours from the time of application, three 
worms of the four were entirely dead, and the fourth was motionless, 
but showed some signs of life when irritated. 
In the next experiment, a much smaller quantity of the powder 
was applied to two worms, nearly full grown, and a third about half 
full size. In ten minutes the small worm became uneasy. In an- 
other ten, one of the older ones was likewise affected, while the 
young one was writhing about in pain. In forty-five minutes both 
of the old worms were attacked, while the young one was nearly 
helpless. In an hour and a half the young one was dead, and one 
of the larger nearly so, while the third showed the effects of the 
poison, but in a much Jess degree. In six hours the larger worms 
were crawling about, although somewhat stupid ; but by the next morn- 
ing, that is, in twenty-four hours, both of the old ones had recov- 
ered. 
In the next experiment, a small quantity of the same mixture was 
placed with the point of a knife on the backs of three worms of the 
same sizes as those used in the preceding. In ten minutes none of 
the worms gave any evidence of mjury. In twenty minutes, how- 
ever, the young one and one of the larger were curled up motion- 
less, both exuding a green fluid from their mouths, while the other 
one was crawling about unaffected. In half an hour all of them 
were moving about, although somewhat stupid. In another hour all 
seemed to be recovering, and in six hours no further effect was per- 
ceptible. The worms all finally regained their usual activity. 
Five specimens were then selected, two nearly full-grown, and three 
about five-eighths of an inch in length. They were placed in a shal- 
low dish, and dusted with the pure pyrethrum powder, undiluted 
with flour. This had the usual effect upon the young worms in 
about five minutes, and in seven minutes upon the larger also. In 
fifteen minutes all of the worms were rolling about in a helpless 
condition. In an hour the smaller worms were nearly motionless, 
and the larger growing weaker. In an hour and a half all were © 
apparently dead. 
The preceding notes show the efficacy of pyrethrum, if freely ap- 
plied to the worms, whether pure or diluted with flour, one part. to 
ten. The dilution, however, slightly decreases the energy of its ac- 
tion. In order to determine whether the flour served as a simple 
diluent of the pyrethrum powder, or whether it absorbed and retained 
a part of the volatile and active principle of the plant and thus 
become itself an efficient insecticide, I wrapped a small quantity in 
a cloth, and imbedded it in a jar of pyrethrum powder, leaving it 
there for three days. It was then removed and dusted upon four 
cabbage worms, two nearly full grown, and two about half grown. 
In twenty-four hours the two smaller worms were dead, and the 
other ones unaffected. It is evident, therefore, that the flour absorbs 
a part of the active principle from the pyrethrum. 
