572 Insect Powder. [September, 
INSECT POWDER. 
BY WILLIAM SAUNDERS. 
HE insect powders of commerce are the powdered flowers of 
different species of Pyrethrum. Those of Pyrethrum carneum 
and roseum were introduced some thirty years ago under the 
name of Persian Insect Powder, and subsequently those of Pyre- 
thrum cinerarie folium, a native of Dalmatia, Austria, as Dalma- 
tian Insect Powder. Both the Persian and Dalmatian powders 
are good insecticides, but the latter is much the more energetic 
in its action and hence commands a higher price ; indeed, it is so 
much preferred that it is gradually driving the so-called Persian 
powder out of the market. The fact of the flowers of P. roseum 
being less active than those of P. ctheranie folium, has been 
accounted for on the ground that the single flowers are much 
more powerful than the double ones, and that the double flowers 
occur in P. roseum in much larger proportion than in the other 
species. The flowers, either whole or powdered, preserve their 
activity for a long period. A recent European experimenter 
states that he could not perceive any particular loss of activity in 
samples which had been kept six years. The fresh (undried) 
flowers act very slowly as compared with the same dried and 
powdered, and the plant itself powdered is quite inactive. It is 
singular that while there are many other composite plants closely 
related to the genus Pyrethrum, as yet this peculiar property has 
been found only in plants belonging to this genus, and even 
within this limit there are several species whose value as insecti- 
cides is very slight. A large number of Composite indigenous 
to Austria have been tested and found to be of no value in this 
respect. The flowers of Tansy (Tanacetum papere) are said to 
have a slight stupefying effect. 
The Pyrethrums are hardy plants which bloom abundantly the 
šecond year from seed. The powder is prepared from the half- 
opened flowers gathered during dry weather and dried in the 
shade under cover, but the process of gathering, drying and pre- 
paring involves so much time that their culture can only be made 
profitable where labor is cheap. ; 
Insect powders have not attracted general attention as insecti- 
=- cides until within the last three or four years, during which time 
= they have been introduced in various forms in packages an 
