.42 THE CANADIAN ENTOMOLOGIST. 



The Pyrethrums are hardy plants which bloom abundantly the second 

 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 preparing involves so much time that 

 their culture can only be made profitable where labor is cheap. 



Insect powders have not attracted general attention as insecticides 

 until within the last three or four years, during which time they have-been 

 introduced in various forms in packages and boxes, accompanied by suit- 

 able blowers or insect guns for the purpose of properly distributing the 

 powder, and recommended for the destruction of flies, cockroaches, fleas, 

 bugs, &c. Sometimes 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 a room with 

 the doors closed, the discharges directed towards those parts where flies 

 are congregated, will stupefy 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 pow- 

 der, 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 harmless 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 



