DISEASES AND ENEMIES 281 



It is a remarkable fact that the damage done is 

 often very serious, while the number of thrips to be 

 found on the leaves is very small ; very often they are 

 only to be found on the very young leaves. Accordingly 

 the extent of the damage done by this insect is not so 

 much the consequence of their large number, as is- the 

 case with Helopeltis in Java, but of the serious harm a 

 single insect can effect. 



The fruits are also attacked, and grow brownish as 

 they ripen instead of yellow, this being a consequence of 

 the formation of a thin layer of cork on the surface. 

 But they are not damaged in any other way and 

 generally they ripen normally. 



Thrips appears especially in fields where the con- 

 ditions are not very favourable. In times of long 

 drought the insect is especially troublesome, while heavy 

 rains make it sometimes disappear quickly. It is more 

 common on poor soils than on rich ones. 



In Surinam spraying with kerosene emulsion, tobacco 

 decoction, or Paris green was unsuccessful, and a direct 

 way of combating the pest has not yet been found, 

 though in Grenada good results have been reported 

 from spraying with kerosene emulsion. In no country, 

 however, has the application of fungicides against thrips 

 become popular, and more extensive experiments with 

 different mixtures should be undertaken by the Experi- 

 ment Stations. 



Thrips has also been found to do damage, to a greater 

 or smaller extent, to the mango (Mangifera indica), 

 the canary tree (Canarium commune), the cashew 

 (Anacardium occidentals), the guava (Psidium 

 guayava) ; it also lives on the Liberian coffee tree, but 

 apparently without doing harm. 



In Java the "cocoa-moth" (Zaratha cramerella) is, 

 with the Helopeltis, the worst enemy of the cocoa, and 

 on many plantations the loss caused by the moth may 

 be considered to be even greater than that caused by 

 the Helopeltis. 



The small caterpillars of this little moth live in the 



