Entomological Notes. 281 



if it is unadulterated and fresh, which cannot be said in many 

 instances of the powder sold at retail by our druggists, it may be 

 considerably diluted with other pulverized material without 

 losing its deadly effect, the use of the powder thus becoming 

 much cheaper. Of the materials which can be used as diluents, 

 common flour seems to be the best, but finely sifted ashes, saw- 

 dust of hard wood, or any other light and finely pulverized 

 material that mixes well with the powder, will answer the 

 purpose. 



If the mixture is applied immediately after preparation, it is 

 always less efficacious than when left in a perfectly tight vessel for 

 about twenty-four hours, or longer, before use. This has been so 

 far only with the mixture of Pyrethrum with flour/but doubtless 

 holds true with other diluents. Mr. E. A. Schwarz experimented 

 largely under our direction with the mixture of Pyrethrum and 

 flour for the cotton worm, and he found that one part of the pow- 

 der to eleven parts of the flour is sufficient to kill the;- worms 

 (only a portion of the full-grown worms recovering from the 

 effects of the powder), if the mixture is applied immediately after 

 preparation ; but if kept in a tight glass jar for about two days, 

 one part of the powder to twenty-two parts of flour is sufficient 

 to kill all averaged sized worms with which it comes in contact. 

 For very young cotton worms, a mixture of one part of Pyreth- 

 rum to thirty parts of flour, and applied one day after prepara- 

 tion, proved most effective, scarcely any of the worms recovering. 



An ordinary powder bellows will answer for insects infesting 

 dwellings, or for plants kept in pots in rooms, or single plants in 

 the garden, but it hardly answers on a large scale out of doors, for it 

 works too slowly ; the amount of powder discharged cannot be regu- 

 lated, and there is difficulty in covering all parts of a large plant. 

 Another method of applying dry powder is to sift it on to the 

 plauts by means of sieves. This method is no doubt excellent 

 for insects that live on the upper side of the leaves ; for large, 

 shrub-like plants, and for insects that live or hide on the under 

 side of the leaf, it will prove less serviceable. A very satisfac- 

 tory way of applying the powder on large plants, in the absence 

 of any suitable machinery or contrivance, is to throw it with the 



