66 EXPERIMENT STATION KECOKD. 



it are insoluble in ammonia. This test is valuable, but can not be 

 depended upon in all cases. If a small quantity of the Paris green 

 ])e placed upon a glass slide and the glass jarred so as to cause the 

 Paris green to slide down the surface of the glass, a bright green track 

 will be left behind if the sample is pure, whereas the track will he 

 white or pale green in case it is impure. The most satisfactory test, 

 however, is the microscopic one. Under the microscope Paris green 

 appears in the form of clean round masses. In impure samples one 

 readih" observes in addition to these regular spheres quantities of mate- 

 rial of irregular crystalline shape, usuall}^ of paler color. 



In New York, Louisiana, Texas, and Oregon laws have been enacted 

 recjuiring Paris green to contain 50 per cent of arsenious oxid. A 

 great defect of these laws is that no attempt is made to distinguish 

 between soluble and insoluble arsenious oxid. A very low grade of 

 Paris green may, therefore, be made to contain a sufficient quantitj^ 

 of arsenic ])y simply adding arsenious oxid, which is cheaper than 

 Paris green. The standard which has been adopted by the station 

 makes the following requirements: "(1) The sample will be expected 

 to contain, as seen under the microscope, only a trace of foreign mat- 

 ter; (2) the total arsenious oxid shall exceed 50 per cent; (3) the sam 

 pies shall contain practically no free arsenic or other soluble arsenical 

 compound.'" 



Paris green has proved a satisfactory insecticide against the codling 

 moth when a standard quality is used. The substance has, howev^er, 

 become so unreliable that it seems advisable in the opinion of the 

 author to use some substitute. Arsenite of copper has been used in 

 various localities with considerable success. Barium arsenite was 

 found unsatisfactory, being easily soluble and injurious to the foliage. 

 London purple is the oldest substitute for Paris green, but it often 

 contains considerable free arsenic so as to make it injurious to the 

 foliage. Arsenite of lime has been used in several States with good 

 results. Arsenite and arsenate of lead have been used by the Gj'ps}" 

 Moth Conmiission as a substitute for Paris green. The arsenate of 

 lead is decidedly the better substance for the gypsy moth and is per- 

 haps to be preferred. Practical directions are given for preparing 

 arsenate of lead, arsenic and lime, and arsenic, soda, and Ijme. 



The authoi' gives a brief discussion of various other methods for 

 fighting the codling moth, among which mention may be made of the 

 })and treatment, the destruction of windfall a})[)les, destruction of the 

 codling moth in storage houses, the use of traps for the destruction of 

 the moth, scraping the bark, and th(; application of winter sprays. 

 Attention is called to the fact that one application of an insecticide is 

 not sufficient. The spraying should be repeated during the summer 

 at intervals of 3 or 4 weeks. It is necessary to take account of dif- 

 ferences in the habits of the moth in different localities and during 



