RUBBER 625 



stems made no attempt to feed upon the bark. It must 

 be remembered, however, that the larvae of many 

 Elaterids, under the popular name of " wire-worms," are 

 recognized as agricultural pests of some importance. 



In the Cerambycidae or Longicorns we have at least 

 one serious pest. This is the large and handsome 

 Batocera rubra, the larva of which tunnels into the tap 

 root and stems of well-grown Hevea trees. The insect 

 is indigenous in Ceylon, but has only recently attracted 

 attention as a rubber pest. Isolated cases of injury by 

 some large borer have been reported at intervals for the 

 last seven or eight years, but all attempts to determine 

 the adult insect proved unsuccessful until 1912, when the 

 species was finally identified. The injury may take two 

 forms, either central or peripheral. In the former case 

 the centre of the tap root is hollowed out, and the tunnel 

 may extend well up into the base of the stem, increasing 

 in diameter as the grub grows larger. In the second 

 case the attack is from the outside, usually at or just 

 below ground level. Occasionally the point of entry may 

 occur higher up on the stem. Irregular cavities are eaten 

 through the bark and into the wood of the tree. Some- 

 times the injury is confined to the outer parts; at other 

 times a tunnel is driven right into the heart of the tree. 

 It is possible that these two forms of injury may be due 

 to the work of two distinct species of beetles, but I have 

 been unable to detect any difference in the larvae. The 

 symptoms of attack are usually obscure. There may be 

 a gradual loss of foliage, but this is not readily distin- 

 guishable from the natural periodic defoliation. When 

 the injury is below ground level, the first intimation may 

 be the collapse of the tree, which frequently breaks off 

 at a point a few inches below the collar. Or, in sheltered 

 situations, the tree may gradually die and dry up. When 

 the 'Stem is attacked from the outside, at or above the 

 collar, the wound may be discovered by an oozing of 

 diseased sap. There is no* very noticeable extrusion of 

 excreta, much of this matter being retained in the tunnel. 

 The method of entry, in cases of external attack, is a 

 comparatively simple matter. The eggs are deposited in 

 deep cavities of the bark and in wounds, especially such 



