64 



GENERAL TREATMENT OP INSECT PESTS. 



This paper contains brief directions as to the means to be adopt- 

 ed for the destruction of garden and crop pests. In such small 

 space elaborate methods, applying to special cases, cannot be dis- 

 cussed but the directions given may be modified with discretion 

 and rendered applicable to ordinary insect diseases. Many of the 

 remedies described are derived from the published work of ento- 

 mologists in other parts of the world and are such as have been 

 found to give the best result under the conditions obtaining in the 

 West Indies. 



Determination of the cause of Disease. 



When a plant is supposed to be diseased, it should be carefully 

 examined to find the cause of the injury and any unusual appear- 

 ance should be noted. There may be some difficulty in discover! 

 ing, with certainty, the real source of damage but a thorough exam- 

 ination of the plant, in cases where the disease is not at once 

 apparent will, as a rule, reveal the true nature of the injury and its 

 cause. It is of no use to assign the damage to the first or to any 

 insect that may be found on the plant, and if treatment is adopted 

 for the wrong class of pe.-t the best results are not likely to be 

 obtained. 



Insect Pests. 



Plants are attacked by diseases and pests of very various kinds, 

 of which insects form a large proportion. Speaking generally, 

 harmful insects may be divided into three classes according to 

 their mode of attack : — 



(1) Leaf-eating insects. 



(2) Boring 



(3) Sucking 



Leaf-eating Insects may be taken to include those that feed on 

 the leaves and other exposed parts of the plant. Caterpillars 

 (" worms ") are the most common, and grasshoppers often do a 

 considerable amount of harm. A well known instance of caterpil- 

 lar attack is found in the Para Rubber tree whose leaves are some- 

 times eaten by large numbers of caterpillars. Other familiar in- 

 stances are the caterpillars that attack the water-lemon vine, canna, 

 arrowroot, tobacco, sweet potato and cassava. As a rule each 

 kind of caterpillar confines itself to one food or to closely related 

 plants. 



Boring Insects feed inside the tissues of plants, spending the 

 greater part of their lives securely hidden. All parts of plants are 

 attacked, the plaintain weevil living in the roots or in the part of 

 the stem below the ground, the cocoa beetle tunnelling in the 

 trunk and branches, and the coffee-leaf miner boring in the leaves 

 are familiar examples. Other boring insects live in dried grain, 

 tobacco, nutmegs, furniture, etc. 



Sucking Insects are, at the present time, the most destructive 

 insect pests in the West Indies. They include the plant lice 

 (Aphidae) the mealy-wings (Aleurodidae), and the scale insects 



