RU15B1' R 609 



to a large extent protected from insect attack by the 

 copious flow of viscid latex that exudes from the slightest 

 wound to the cortex. Small insects that rashly try to 

 penetrate the stem are either engulfed in this fluid or 

 repelled from further attempts in that direction. Dr. 

 Wurth, experimenting with Xyleborus coffea? (one of the 

 so-called " shot-hole borers ") in Java, placed some of 

 the beetles on a green Hevea twig, and has described the 

 results as follows: "Most of the beetles began boring 

 at once, but the hole was scarcely half a millimetre deep 

 before a drop of latex appeared, which coagulated, and 

 thereby stuck the beetle fast and killed it. In a short 

 time there were more than thirty beetles fast, and 

 looked as though they had been caught on a limed stick." 



Sucking insects, however, drawing their nourishment 

 from the sap of the plant, are able to reach their objective 

 without interference with the laticiferous vessels. Coccidse, 

 for instance, possess hair-like haustella which they are 

 able to introduce into the tissues of the plant, and to 

 guide in any desired direction to a distance considerably 

 longer than their own bodies. 



This comparative immunity does not extend to the 

 foliage of the plant where the latex is greatly reduced in 

 quantity. Nor is it proof against the larger animals. 

 Indeed, the latex itself appears to be the principal attrac- 

 tion in some cases. It might be thought that a fluid 

 which, when coagulated, is transformed into solid rubber 

 would seriously inconvenience the internal economy of 

 any animal. But this does not appear to be the case. 

 Possibly the digestive fluids prevent coagulation or alter 

 the substance in such a manner as to render it digestible. 

 I have been credibly informed, though I am not in a 

 position to vouch for the fact, that even man himself 

 may imbibe considerable quantities of rubber latex with 

 impunity. 



By far the greater proportion of insects that are known 

 to attack the Hevea tree are really secondary pests, i.e., 

 pests that follow upon a diseased or unhealthy condition 

 of the tree resulting in a diminution or complete cessation 

 of the protective latex. In this connection I speak of 

 the latex as " protective," not that I wish to assert that 



