THE DISEASES OF THE SUGAR-CANE. 465 



thereby of the carefully fostered moisture-yielding humus. 

 Consequently this method is not recommended or adopted 

 excepting in extreme cases. ^ 



4. A more promising field of activity seems to be opened 

 up in the encouragement of the enemies of parasites. We 

 know, for instance, that the moth-borer itself has many 

 minute enemies which feed upon it and tend to keep it in 

 check.^ Is it possible so to increase these latter as to 

 render the very existence of the moth-borer doubtful ? 



But success in this direction is accompanied by many 

 difficulties, and needs comprehensive knowledge of the 

 interdependence of the various forms of animal and vege- 

 table life. 



One of the most interesting examples of this class of 

 remedies is the recent introduction of the Mongoose from 

 India to the West Indies, for the purpose of ridding the 

 fields of the swarms of rats which destroyed great quantities 

 of ripe canes. The experiment, suggested so long ago as 

 18 14 by Lunan,^ may be regarded as having been success- 

 ful in the main ; although its most ardent supporters cannot 

 claim that the success has been unqualified. The rats have, 

 it is true, disappeared from the fields ; but the mongoose, 

 having enormously increased in numbers, has turned its 

 attention elsewhere for food. Not only are the poultry- 

 yards boldly attacked, but game and all sorts of ground 

 birds and lizards have almost disappeared. Urgent appeals 

 have now been addressed to the Governments of various 

 islands to take measures to destroy the mongoose. Its 

 introduction has disturbed the balance of nature. The 

 native insect-destroyers have been decimated, and many 

 see in this one rash step the cause of all the ills of the cane- 

 fields ! The introduction of a few pairs of mongoose has 

 produced results neither dreamt of nor desired, but probably 

 legislative action will be futile. The animals have apparently 

 reached their limits as regards numbers, and the judicious 

 introduction of tree-nesting insectivorous birds might do 

 much towards recovering an equilibrium.* 



An interesting attempt is recorded to inoculate the rats 



^ Harrison (i). - Barber (i), p. 308. ^ Lunan. ^Mongoose. 



