274 Forty-fifth Report on the State Museum. 



nell r^niversity, Ithaca, N. Y. The first part only of this (price 

 two dollars) has been published. Application for it should be 

 made to the author. 



Learn of Insecticides amniow to Use them. — The publications 

 above named, and notably those of the department at Washington, 

 will give the needed information in this direction. The recent 

 advance in economic entomology has been largely through discov- 

 eries of insecticides, and the invention of apparatus for theii' easy 

 application. Of our best insecticides in use at the present are 

 white hellebore, Paris green, London purple, pyrethrum, kerosene, 

 and tobacco. It is essential that one should know how, when, and 

 in what proportions these are to be applied, the proper dilution 

 of those that require it, and the method of emulsifying kerosene. 

 It is also important that the relative value of wet and dry mixtures 

 and the mosit economical and effective method of application 

 should also be known. The great practical value of a reliable 

 insecticide was years ago taught us in the discovery of the method 

 of destroying the Colorado potato beetle, which threatened at first 

 to arrest potato culture in our country. More recently it® value 

 has again been clearly demonstrated in the use of the arsenites 

 (Paris green and London purple), sprayed upon the forming fruit 

 of our apple trees for protection from the apple-worm of the cod- 

 ling-moth. There is no longer question but that, by a proper 

 use of either of the above named arsenites, at least three-fourths 

 of the apple crop can be saved from the codling-moth. Worm- 

 eaten apples should henceforth be a discredit and a disgrace to 

 the fruit-grower, and each worm-hole a stamp attesting to his ignor- 

 ance or inexcusable neglect. 



For the judicious use of insecticides, it is important that recog- 

 nition should be made of two classes of insects — those that take 

 their food by means of biting jaws> and those that feed only on 

 the sap of plants through a proboscis inserted ia the bark. The 

 fonner, which includes the larger proportion of insects, can be read- 

 ily poisoned by the application of the arsenites to the foliage which 

 they consume. The latter, consisting of the Hemiptera, such as 

 the plant-lice (Aphides), bark-lice, and all bugs properly so-called, 

 which imbibe theu' liquid food from beyond reach of the poison, 



