306 ANNUAL OF SCIENTIFIC DISCOVERY. 



fifteen inches in height, bearing flowers an inch and a half in diameter, 

 and resembling those of the ox-eye daisy (Chrysanthemum Leucanthe- 

 mnm). Its cultivation is easy, and its appearance quite ornamental. 

 It flowers from June to September, and may be propagated by layers 

 as well as by seed. 



The parts of the plants from which the powder is made are the dried 

 flower-heads, gathered when ripe, on fine days, and dried by exposure 

 to the sun. In the process of desiccation they lose about 90 per cent. 

 When perfectly dried, they are reduced to powder. 



A quantity of these plants grown upon eighteen square rods is esti- 

 mated to furnish one hundred pounds of powder, which is best pre- 

 served in sealed vessels of glass. The application is made either as a 

 powder or as an infusion, though in the latter form it is more beneficial, 

 especially when intended for the destruction of insects on plants. The 

 powder may be employed directly to the insects themselves, or in the 

 places which they frequent. They are attracted by its smell, become 

 stupefied, and immediately die. This substance may be employed 

 without injury to the larger animals, or to man. It is intimated that 

 the amount of this powder consumed annually in Russia alone is about 

 500 tons. 



The principal insects to which the powder of the Pyrethrum is de- 

 structive, may be arranged under four classes, --first, insects injurious 

 to agriculture and horticulture ; second, insects obnoxious to man and 

 his habitation ; third, insects destructive to certain substances, as wool^ 

 furs, feathers ; and, fourth, insects injurious to museums of animal and 

 vegetable products, and collections of natural history. We do not pre- 

 tend to enumerate all the insects to which the powder is destructive ; 

 it will suffice to mention a few instances, which will sufficiently show 

 what applications may be made of it. Our domestic animals, dogs, 

 cats, fowls, pigeons, etc., are subject to annoyance from insects, 

 which cannot withstand the effects of this powder. Of the numerous 

 insects injurious to agriculture and horticulture we may mention the 

 following which have been destroyed by it : the weevil, bark-beetle, 

 wheat-fly, maggots, cocci, aphides, earwigs, spiders, ants, etc. It is 

 evident that not only the perfectly developed insects are destroyed, but 

 also the larvae, which in some cases do greater injury than the insects 

 themselves. Large depots where military stores or navy supplies are 

 kept, and especially extensive bakeries, may use the powder with great 

 advantage for the destruction of weevils, midges, crickets, cockroaches, 

 etc., the great plague of those establishments. The powder is equally 

 efficacious in destroying insects which are a constant source of annoy- 

 ance to the inhabitants of cities and the country. Gnats and mosqui- 

 toes are* banished ; bugs, fleas, and flies disappear from houses under its 

 influence. 



The powder of the Pyrethrum applied to furs, feathers, woolens, ob- 

 jects of natural history and botanical herbariums-, acts also as a complete 

 protection against insect ravages, while as regards the human subject 

 it is perfectly innocuous. In using the powder, says M. Willemot, it 

 must be applied carefully and in sufficient quantity, otherwise the re- 

 sult will be unsatisfactory, especially if used against some of the hardy 

 or very resisting species of insects. Occasionally the powder, by being 

 exposed to the air or moisture, will have lost its destructive properties, 



