62 The Tea insects of India. 



With regard to the amount of dilution required, a mixture of twelve 

 parts of water to one of emulsion has been recommended in America 

 as a safe wash for ordinary purposes. In Ceylon^ Mr. Green has found 

 so weak a wash as one part of kerosine emulsion to eighty parts of water 

 sufficient when applied in the eveniug to kill aphids and mites upon 

 the tender shoots of tea plants in nurseries. He recommends that even 

 this should be followed with a washing of water the next morning 

 if no rain intervenes in the night. It will probably prove, however, 

 that very much stronger applications can be used with safety, without 

 subsequent washing, especially upon the older bushes, when the necessar}' 

 precautions are taken to apply in a very fine spray when the sun is off 

 the plants. . 



Arsenical Insecticides. 



The best known of these useful insecticides are Paris green and 

 London purple respectively. Without going into the question of their 

 chemical structure, it is sufficient to say that they are brightly coloured 

 substances which are exceedingly poisonous, not only to insects but 

 also to ail forms of animal life. On this account they were for a long 

 time looked upon with very considerable distrust. Of late years, how- 

 ever, it has been shown that when properly used the amount of poison 

 which it is necessary to distribute is so small that with ordinary care 

 they can be used with entire safety. As the result they are now em- 

 ployed upon a very considerable scale, especially by fruit-growers in the 

 United States. 



Like kerosine emulsion they require to be diluted to an enormous 

 extent with water and applied to the foliage in the foim of an exceed- 

 ingly fine mist-like spray. The poison is thus distributed over the 

 leaves and acts, not like kerosine emulsion by actual contact with the 

 insects, but by poisoning the leaves upon which they feed. Paris ^reen 

 and London purple are thus principally effective against such caterpillars, 

 grasshoppers, and beetles as actually eat the substance of the leaves, 

 and are less useful against species which feed by sucking up the juices 

 of the plant by means of a proboscis. It may be noticed, however, that 

 satisfactory results have been obtained with London purple ^ in the 

 Saharunpore Botanical Gardens, North- West Provinces, not only against 

 caterpillars but also against a Jassid which attacks the flower of the 

 mango tree, and which is closely related to the green fly blight of tea. 

 In this case the precise action of the wash is somewhat difficult to ex- 

 plain. 



^ Vide his pnpers in the Ceylon Independent. i 



' The London puiple experimcntpd with in this case had been furnished to the 

 India Museum by Messrs. Hemingway & Co., of 60, Mark Lane, l-ondon, E. C. 



