RUBBER 629 



Xyleborus scmigranosus. (Ceylon.) 



,, semiopacus, boring in dead stems. (Ceylon, 



F.M.S.) 



,, submarginatus. (Ceylon.) 

 Cryphalus plumierix, in dead stems. (Ceylon.) 

 ,, congonus. (Belgian Congo.) 



,, kevese. (Belgian Congo.) 



,, tuberculosus. (Belgian Congo.) 



Platypus s'olidus, in diseased stems. (Ceylon.) 

 Eccoptopterus sexspinosus, in dead and diseased 

 branches. (Ceylon.) 



Phlceotribus puncticollis. (South America.) 

 Coccotrypes sp., in dead leaf-stalks. (Ceylon.) 

 It is not surprising that the list is a long one, and it 

 could probably be greatly extended. It should be under- 

 stood, however, that, though all these boring beetles 

 were found in Hevea stems, it does not follow that they 

 are equally concerned in injury to the tree. In many 

 cases the trees had been dead for 'some considerable time. 

 In the tropics, such dead trees are rapidly infested 

 by boring insects of various kinds. It is, indeed, 

 doubtful if any of these small beetles can penetrate the 

 healthy bark of a rubber tree without being hopelessly 

 involved in the viscid latex. I have frequently found 

 dead beetles embalmed in a clot of coagulated latex 

 victims of rash experiment. But should anything cause 

 a permanent or temporary cessation of the production of 

 latex, such insects immediately seize their opportunity. 

 Both Bostrichidae and Scolytidae are strongly attracted 

 by bark or wood that has been infected by canker and 

 other fungoid diseases. Hevea trees are subject to several 

 serious fungoid diseases, including a canker very similar 

 to that of the cocoa. In no instance have I found borers 

 in sound, healthy bark. A healthy rubber tree is self- 

 protected from boring insects by its own laticiferous 

 secretions. In the incipient stages of canker only the 

 superficial layers of bark are involved. Borers will attack 

 these spots and will attempt to gain an entrance; but, as 

 soon as they reach the deeper and, as yet, unaffected 

 layers, they are repelled by a flow of latex. In later 

 stages of the disease, when the whole thickness of the 



