Clje Canadian Entomologist. 



VOL. XI. LONDON, ONT., MARCH, 1879. No. 3 



INSECT POWDER. 



BY THE EDITOR. 



The 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 Pow- 

 der, and subsequently those of Pyrethrum cineraria folium, a native of 

 Dalmatia, Austria, as Dalmatian 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. cinerarice 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 for six years. The fresh (undried) flowers act very slowly 

 as compared with the same dried and powdered, and the plant itself pow- 

 dered is quite inactive. It is singular that while there are many other 

 composite plants closely related to the genus Pyret/irum, 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 Composites indigenous to Austria 

 have been tested and found to be of no value in this respect. The 

 flowers of Tansy ( Tahacetum vulgare) are said to have a slight stupefying 

 effect. 



