16 THE AGRICULTURAL PESTS OF INDIA. 



to Ceylon. Professor Westwood, of the Oxford Univer- 

 sity Museum, in January 1885, revised what I had 

 then written as to destructive insects ; and Mr. Water- 

 house, of the British Museum, revised nearly the whole 

 in manuscript and the proofs as they passed through the 

 press. The article ' Coleoptera ' is from his pen, and 

 that on ' Fishes ' is chiefly by Dr. Francis Day, C.I.E. 



The alphabetical arrangement has been adopted for the 

 contents, that being deemed the most suitable form in 

 the present state of our knowledge. 



The people of India are skilled in the use of all the 

 implements of husbandry, and in applying manures 

 economically, although in the latter they are far excelled 

 by the Chinese. But in protecting their crops and in 

 cleanly cultivation, India is greatly behind. 



One of the protective measures against insect ravages, 

 which is strongly urged on cultivators in all countries, is 

 to change the crops in successive years. Each insect 

 species has its own particular plants on which alone it 

 lives, and when deprived of food by a change in cultiva- 

 tion, they die. The cucumbers, the rice and cotton 

 plants, the tea and coffee shrubs, the bamboo, the sal, 

 pine, and fir trees, have each their own enemies ; and on 

 land where a rotation of crops is followed, the parasites 

 have to seek fresh marauding ground once a twelve- 

 month or oftener, and are frequently kept away entirely 

 or for a considerable period by an absence of their special 

 food. Mr. Scott says that a steady system of rotation of 

 cereals generally with the pulses, would to a certainty 

 impair the fecundity of the chief ravagers of the food 

 crops, the grub, maggot, and caterpillar forms, as few 

 of the insects with which the cultivated crops have to 

 contend find a common food- stuff on the cereals and 



