286 CACAO 



in situations where the climatic conditions are favourable. 

 In such cases the insect seldom or never gets beyond control 

 sufficiently to become a pest. 



We know, again, that insects of this class are also 

 controlled by insect parasites and by predatory insects, 

 which feed upon and destroy them, a familiar instance of 

 which is seen in the destruction of insects by the Lady Bird 

 beetles, or Coccinellids. 



The larvae of some flies also feed upon aphides, plant lice 

 or " blight," and there are numerous instances where 

 insects of the sub-order aculeatce (the wasp family) feed 

 upon and destroy in large numbers insects which are 

 injurious to plants or destructive to vegetation. 



The application of remedies, washes, &c., is always open 

 to disappointment of some kind. The wash may be 

 improperly compounded. It may be too strong or too weak, 

 in the former case causing destruction of vegetable tissue, 

 and in the latter a waste of time, labour, and material 

 in applying inert material. 



There can be no doubt, therefore, that where possible 

 Nature's methods are by far the best, and that the greatest 

 progress in control work will be made in the search and 

 discovery of means of natural control, which Nature, in 

 most cases, places close to hand in waiting for discovery. 



A recent writer says : * " Extraordinary multiplication 

 is counterbalanced in Nature by the predatory or parasitic 

 habits of species of the same class." He also writes : 

 " Resort to artificial methods, such as the use of insecticides 

 in combating cotton pests, has not been much advised for 

 'practical reasons, but if their use should become necessary, 

 and it were shown that they could be used effectively, the 

 question of practicability might disappear." (Italics ours. 

 — Author.) 



The question of control under certain carefully devised 



cultural conditions and the question of susceptibility of 



certain plants to attack are both well worthy of the closest 



study, as it would appear that certain conditions of health 



* D. T. ITuUaway, Hawaii Experiment Station (Bull. 18). 



