70 N. S. ENTOMOLOGICAL SOCIETY 



had become quite general. This marks an important mile- 

 stone in insect control; and is regarded as the commencement 

 of modern methods of artificial control by insecticides. 



Paris green is the most commonly used arsenical poison 

 at the present time. In Canada it is used more than all other 

 arsenicals combined. It is largely used because of the great 

 reputation it has had in the past. Eminent chemists have 

 termed Paris gresn "an absurdity,'' while others have predicted 

 that with education the public would turn from it. For the 

 fact is that Paris green is a very expensive form in which to buy 

 arsenic, and that it has very few saving graces, which warrant 

 its continued use. The acetic acid used in its manufacture 

 serves for little else than to give it its typical color. On foliage 

 Paris green is always liable to give some burning, unless used in 

 Bordeaux mixture, nor does it adhere well nor remain readily 

 in suspension in water. 



In Nova Scotia Paris green is not used proportionately to 

 the same extent as in the rest of Canada. It has largely been 

 displaced by either cheaper or safer arsenicals. 



Lead Arsenate. 



Lead arsenate was first made for use as an insecticide in 

 1892, by F. C. Moulton, a chemist in the employ of the Gypsy 

 Molh Commission, in Massachusetts. It was deliberately 

 developed for a definite purpose, namely, as an insecticide 

 which could be used alone, and at all strengths, on ordinary 

 foliage, without producing injury. It was used first in 1893, 

 after which it became well known. The effect of the discovery 

 of lead arsenate hardly needs comment; it serves its purpose 

 eminently in the control of the Gypsy moth, and also of the 

 Brown Tail moth, and without it the damage inflicted by both 

 of these insects would have been incalculably greater. Lead 

 arsenate was frequently known as Gypsine, derived from the 

 Gypsy moth, and also as Disparine, derived from Porthetria 

 dispar. 



Lead arsenate is at present used for the purpose for which 

 it was made, as an insecticide for use on all kinds of foliage and 

 at all strengths. It is the insecticide par excellence for the 

 control of heavy outbreaks of biting insects. Used in exces- 

 sive strengths it is very effectual. It is the least injurious of 

 all arsenicals to foliage when used alone, it has great powers of 

 adherence, and remains readily in suspension in water. It is 

 essentially the insecticide to use, when it is desirable to use an 



