100 SOME SOUTH INDIAN INSECTS, ETC [CHAP- XI. 



When used as a spray, eight to ten ounces of Paris Green are used 

 in 100 gallons of water to which have been added two pounds of 

 lump Lime to neutralize any soluble arsenic. The advantages of 

 Paris Green are its cheapness and powerful poisonous action ; 

 amongst disadvantages may be noted the fai t that it is not properly 

 held in suspension in the sprayer without constant agitation and 

 there is therefore risk of uneven application, that it sometimes 

 burns the plants, and that it is liable to be washed off them very 

 easily. If nut obtainable, it is readily made by dissolving sepa- 

 rately 4 lb. of white arsenic in 5 gallons of water anil 5 lb. of 

 Verdigris in 5 gallon-- of water and mixing the two liquids, which 

 are then boiled for some time anil a little Acetic Acid added. 

 Commercial Paris Green should contain not less than 55 per cent, 

 of arsenic (As, O ), of which only about 5 per cent, should be 

 soluble in water, and about 27 to 31 per cent, of Cupric Oxide. 



London Purple is simply Calcium Arsenite, and derives its name 

 from the fact that the arsenite of lime formerly used was the residue 

 from the manufacture of magenta and was therefore tinted with 

 colouring matter, which, it is needless to add, is not necessary for 

 it- efficacy. Calcium Arsenite is readily prepared by dissolving 

 one pound of white arsenic in two gallons of water and mixing 

 with a solution containing two pounds of lime. The mixture is 

 then heated tor half-an-hour and diluted to make 100 gallons. 

 Calcium Arsenite is insoluble in water and therefore will not burn 

 foliage, but care should be taken to see that the lime is in excess. 

 The original London Purple, however, was variable in composi- 

 tion and this insecticide is not much used at the present day. 



When the foregoing insecticides an not available, ordinary 

 metallic paints are usually obtainable locally in a finely powdered 

 state and may be dusted on dry mixed with lime, Hour, or road- 

 dust ; such paints as red lead, white le.nl. iron oxide, yellow ochre, 

 red ochre, lemon chrome, burnt sienna, etc., may be used in this 

 way, being simply dusted on to the crops whilst these are wet with 

 dew by means of a cloth bag. 



In some eases it ,s necessary to spray vegetables or fruits which 

 are required for consumption within a short period and under such 

 conditions it would obviously In- extremely' dangerous to usearseni- 

 cals or other poisons which might remain on the crop and poison the 

 consumer. In such cases, a temporary insecticide, such as Naph- 

 thaline Emulsion, maj be used, as this acts .is .1 stomach-poison to 

 any caterpillars which may be doing damage and all evaporates 

 away within about twenty-four hours so that the sprayed material 

 may safely be eaten afterwards. It is prepared by dissolving six 



