PESTS. 59 



surrounded by a brownish protuberance from which the repro- 

 ductive form of the fungus is produced. 



With a view to extermination all infected leaves should be 

 collected and burnt. 



INSECT PESTS. 



Healthy Hevea trees are to a very large extent self-protected 

 from insect attacks by the viscid latex which exudes when the 

 bark or epidermis is injured. In the majority of instances where 

 bark-eating beetles have proved injurious to Heveas it has been 

 observed that the tree's vitality had been first lessened through 

 some other cause. Green placed a number of Longicorn bark- 

 eating beetles in a large cage, together with a healthy young 

 Hevea plant. They bit the bark of the plant, causing the latex 

 to flow over their mouths, which they did not appreciate. They 

 relinquished the attack and endeavoured to clean away the 

 viscous fluid. During seven days' confinement without food no 

 further attempt was made to feed on the plant. But upon 

 being placed in another cage with partially dried rubber plants 

 and twigs of non-laticiferous trees they commenced to feed 

 voraciously. 



Although it has not been definitely decided whether latex 

 does or does not play an important part in the nourishment of 

 Hevea trees, there is not the slightest doubt that it is a valuable 

 factor in protecting the plant from insect pests. It is therefore 

 imperative, if advantage is to be taken of this natural protection, 

 that the tree should be maintained in a healthy state and not 

 denuded of latex through over-tapping. Wood exposed by 

 careless tapping is devoid of latex and consequently more 

 susceptible to insect attacks, as also are seedlings which, in 

 process of transplanting, have been allowed to wilt either through 

 being left out of the ground for a long time and their roots and 

 leaves unduly exposed or are planted during protracted dry 

 seasons without irrigating. 



It is important to bear in mind that many insects pass 

 through three stages. From eggs are hatched caterpillars or 

 grubs. These eventually change to a pupal or resting stage, i.e., 

 chrysalis, from which the " perfect insect " (butterfly, moth, or 

 beetle, &c.) emerges. It is generally in the larval or caterpillar 



