44 REPORT ON THE DISEASES Or SILKWORMS IN INDIA 



thing can be achieved in this direction. In any case such work 

 can only be profitably undertaken by one trained in genetics — ■ 

 the subject is much too specialized for anyone else to make a 

 success of it. 



What seems to me a much more profitable line of work is the 

 attempt to determine what external conditions help or hinder the 

 caterpillar in its resistance to disease. Here we are dealing with 

 external factors which are always varying a little from year to year, 

 from place to place. In consequence of this the details would have 

 to be worked out for different districts, and experiments would 

 have to be continued for long periods. It is work which should be 

 undertaken by the sericultural departments of the different provinces 

 interested in sericulture — only the broadest outline can be attempted 

 here. 



It may be taken for granted that anything that tends to improve 

 the general condition of silkworms will make them better able to 

 resist the attack of Nosema bombycis. Improvements in environ- 

 ment should really aim at making the surroundings healthy, 

 as like open air conditions as possible, for we have repeatedly 

 emphasised the fact that under wild conditions it is practically 

 certain that the host suffered little or no inconvenience from the 

 parasite. 



What then are the conditions in nature that we can hope to 

 imitate under domestication ? There are three main features of the 

 wild life of caterpillars that we can try to copy. 



1. Comparative freedom from contaminative infection. Things 

 in nature are comparatively clean. Infective material is at once 

 exposed to the action of the sun, bacteria, various scavenging 

 animals, etc., and thus soon is rendered innocuous or removed. 

 Besides which, as caterpillars are not crowded as a rule very closely 

 on their food plants, and as the plants themselves are scattered, 

 ; nfec'ive material is distributed very sparingly over a large area 

 and the risk of mass infection is reduced almost to a quite negli- 

 gible factor. 



A great deal can be done by rearers to secure in their houses at 

 least an approximation to the above conditions. The danger of 

 infective material can be considerably lessened by the careful re- 

 moval of all faecal matter and litter in general and the storage of the 

 some in a pit, where it should be mixed with other manures for the 

 fields, and if the pit contents are dry they should be sprinkled with 

 water to prevent the formation of dust which could be blown about. 

 The litter should not be fed to cattle nor stored "or burning, as it 

 must be kept dry for these purposes and the dust danger is to be 

 feared. Nor should manure containing silkworm faeces be used to 



