1870. ] Insect Powder. 573 
boxes, accompanied by suitable blowers or insect guns for the 
purpose of properly distributing the powder, and recommended 
for the destruction of flies, cockroaches, fleas, bugs, &c. Some- 
times these prepared articles have been artificially colored so as 
to disguise their source, but all have owed their activity solely to 
the presence of the powdered flowers of one or other of these 
Pyrethrums. 
House flies are very sensitive to the effects of these powders. 
A few puffs of the dust from an insect gun, blown into the air of 
aroom with the doors closed, the discharges directed towards 
those parts where flies are congregated, will stupify and kill them 
within a very short time. The powder is somewhat pungent, and 
to breathe an atmosphere charged with it will frequently cause a 
slight sneezing, but beyond this the operator need not anticipate 
any annoyance. Frequently during the past summer, when flies 
have been troublesome, we have pretty thoroughly charged the 
air in our dining-room and kitchen at night, closing the doors, 
and in the morning found all, or nearly all, the flies lying dead 
on the floors. A few minutes after its use they begin to drop on 
their backs, and after a very short time die; if a room be closed 
for half an hour after using the powder, few, if any, will escape. 
By some this energetic action has been attributed to the presence 
of a volatile oil in the flowers, by other and later investigators to 
a peculiar crystalline principle believed to be an alkaloid; but 
this point does not as yet seem to be fully settled. 
More recently we have been experimenting with this powder 
on the green Aphis which troubles our green-house plants. The 
usual plan of smoking with tobacco is an unpleasant remedy, and 
is also very injurious to many plants of delicate constitution, 
whereas the insect powder, used to any extent, is perfectly harm- — 
less to plant-life. After freely charging the air of a green-house 
with the powder, blowing it in fine clouds of dust among the plants, 
the tiny tormentors who are busily engaged in sucking the life 
out of the leaves and tender shoots, soon manifest symptoms of 
uneasiness and begin to drop from the plants to the ground, and 
in the course of an hour or two the larger portion of the enemy’s 
forces will be found lying sprawling on the earth in the pots or 
on the shelves and floor of the house, where, probably partly 
from the stupefying effects of the powder and partly from their 
Natural inability to find their way to any given point, they fail to — 
