DISCOVERY OF VALUABLE INSECTICIDES. 25 



leaves and the like, will yield to its attraction, aad make hia pilgrim- 

 age even froia the far west, as some have done, to pay his homage to 

 the accumulated treasures of the Eatomological Departtneut of the 

 Agassiz Museum at Cambridge. 



5.. Discovery of Valuable Insecticides. 



Another indication of real progress in economic investigation is the 

 knowledge attained within the pixst few years of several poisons and 

 other substances which may be safely and easily used for destroying in- 

 sect life. Paris green, which holds foremost rank among our Insecti- 

 cides, and without wliich that almost indispensable article of food — - 

 the potato — could not be grown in some localities, was first recom- 

 mended for the purpose in the year 1869, when a correspondent from 

 Wisconsin, of the Galena [III. J Gazette, published the information that 

 the preceding year, with one pound of Paris green mixed with two of 

 flour, sifted through a coarse muslin cloth on the potato tops early in 

 tlie morning, he had destroyed millions of the beetles feeding on them 

 and obtained a fine crop of potatoes.* Pyrethrum had been used for 

 several years under the names of " Persian Insect powder " and "Dal- 

 matian Insect powder," for the destruction of household pests, but it was 

 not until 1879 that it was shown by Mr. Wm. Saunders, of London, 

 Ontario, by his experiments with it upon grasshoppers and plant-lice, 

 tliat it could bo employed in the destruction of insects infesting our 

 fields and gardens, f London purple was first introduced in the year 

 1877.1 ^^ was analyzed by the chemist of the Department of Agricul- 

 ture the folloAving year and found to contain forty-three percent of 

 arsenic acid in such association as to warrant experiments with it as a 

 substitute for Paris green. § The experiments made by the U. S. En- 

 tomological Commission w^ere successful and speedily brought the ar- 

 ticle into popular favor. 'JMie prompt action of oils, such as kerosene 

 oil, coal oil and paraffine oil, in destroying insect life, is well known, 

 and experiments are teaching us the best methods of their application 

 without injury to plant-lifjp. 



The very great value of several of the popular Insecticides, in an 

 economic point of view, warrants a special notice of sonio of them. 



1. Paris Green as an Insecticide. 

 The popularity which Paris green has obtained as an Insecticide 

 grew out of the need of some substance (hand-picking and mechanical 



• *Ame7'ican Enlomologisl, i, 1»69, p. 219. 



^Canadian Entomologist, xi, 1879, pp. 185-G. 

 XNinth Report on the Insects of Missouri, 1877, pp. 45-47. 

 % Annual Rjport of the Cj.n-nissioner of A'jrioultare for 1S16, p. 144. 



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