JTo. 2. ] Notes. 11.5 



Besides reducing the labour of applying the insecticide, force pumps 

 have the further advantage of facilitating the intimate mixture of the 

 soap solution with the kerosine — a condition which, while absolutely essen- 

 tial for the efficacy of the emulsion, is very difficult to obtain by hand. 



The nozzle that is used for spraying the emulsion should be such as 

 to give a cloud of fine spray; this is most important, not only because 

 the same amount of emulsion goes much further when sprayed in a cloud 

 than when sprinkled in drops, but also because a cloud of fine spi*ay has 

 been found to be much more effective than even a heavy drenching in 

 destroying the pest. Dr. Riley supposes that this is because the parti- 

 cles of fine spray adhere, and the whole of the emulsion is thus utilised, 

 while, on the other hand, large drops rapidly run off, carrying most of the 

 kerosine with them, and leaving little but water behind upon the plant. 



The eggs of scale insects have been found to be harder to kill than 

 are the larval and adult forms; two or more light sprayings at in- 

 tervals have been found therefore far more effective than a single heavier 

 application : for the first application kills the larvae and mature insects, 

 and the subsequent ones destroy the larvae that emerge from eggs that 

 have survived the previous treatment. In this connection it is important 

 to ascertain the time that the eggs take to hatch, and also the time 

 required for the growth of the larva?, before they are themselves able to 

 lay eggs; the object being to make the intervals of time between the 

 sprayings ; just long enough to allow all the eggs, that withstand the 

 first application, to hatch out before the second application, while at the 

 same time not permitting any of these larvae to become full grown and 

 to deposit eggs of their own. 



An account of the force pumps and spray nozzles that are recom- 

 mended for applying the emulsion is given in Notes on Economic Ento- 

 mology, No. 2 (1888) ; also in Indian Museum Notes, Vol. I, No. 1, p. 49. 

 The following extract, however, is appended for convenience of refer- 

 ence : — 



" The emulsion is made by mixing two parts of kerosine oil with one part of soap 

 solution or milk (the soap solution being made by dissolving from a quarter to one 

 pound of common soap, or whale oil soap, in one gallon of water). The whole i s 

 violently churned at a temperature of about 100° Fahrenheit, by driving it backwards 

 and forwards through the spray nozzle of a force pump. The emulsion thus formed 

 is diluted with water: — that found successful in the Nilgiris was made with common 

 soap and was diluted, with nine parts of water to one part of the mixture. The wash 

 is applied by spraying it over the affected coffee bushes, and for this purpose an ordi- 

 nary force pump may be used, but it should be fitted with a nozzle that gives a finely 

 divided spray. Probably the best nozzle for the purpose is what is known as the 

 cyclone or eddy nozzle, consisting of a small circular chamber, with two flat sides, the 

 inlet through which the liquid is forced by the pump being bored tangentially 

 through its wall, so as to cause a rapid whirling or centrifugal motion of the liquid, 

 which issues in a funnel-shaped spray through the central outlet in one of the flat 

 sides of the circular chamber." 



