DISEASES AND PESTS 101 



in almost or quite all of the lands where it would other- 

 wise be utterly destructive to the coco -nut industry, 

 and that it is only in occasional outbreaks and these of 

 limited duration that its damage is seriously felt. That 

 other insect pests, among them the sister species 

 Aspidiotus vastatrix, have also been restricted in the 

 same manner, is abundantly proved by experience, in 

 spite of the fact that no pest has ever been exterminated 

 in this way. 



This scale has gradually worked its way eastward 

 over Polynesia, and in some groups of islands as in 

 Tuamotou, has done grave damage. In other islands 

 it is held in check by its natural enemies, and in this 

 way prevented from becoming dangerous. The means 

 of its migration from island to island, as far as is 

 known, are entirely human help. Unhusked coco-nuts, 

 or young seedlings or parts of plants of other hosts of 

 the scale, are carried in boats from island to island, and 

 the living scales are in this way introduced. Under 

 these conditions the obvious method of preventing its 

 spread in this part of the world is by prohibiting 

 the carrying in boats of unhusked coco - nuts or of 

 anything else on which the scale might live. The 

 natives of Takotu and Fakahina have vigorously en- 

 forced a quarantine against the introduction of any 

 living plant, even taro, and by such means have kept 

 themselves immune against damage by the scale. 



In Trinidad Aspidiotus destructor is often pro- 

 tected by the ant Azteca chartifex, and in this way is 

 completely guarded against the attacks of its natural 

 enemies. In such cases the scale insect does considerable 

 damage to coco -nuts. To protect the coco -nuts the 

 planters' business is to destroy the ants, and other 

 insects will then destroy the scales. 



Not less than thirty other species of scale insects 

 have been reported upon the coco-nut. None of these 

 has ever been known to do it serious damage. Whether 

 or not some of them might develop and become de- 

 structive, if not destroyed by other insects, is unknown, 



