REPORT ON THE DISEASES OP SILKWORMS IN INDIA 33 



as that inside a dessicator this figure need not cause excessive 

 alarm. I attempted to reproduce actual conditions (1) by keeping 

 the bodies of pebrinised moths exposed to the air but protected from 

 dust, etc., and feeding this to caterpillars at intervals of 2 and 3 

 months ; (2) by using infected Jcutcha houses and keeping' worms 

 in them until infection almost or completely stopped. Under 

 normal conditions during the hot weather it seems as if material 

 remained infective for at least two months but not for three 

 (Experiments 8 and 9). In the rains, especially towards the latter 

 part, the risk of persistence of infection seems to be greatest — 

 infection being got in a house nearly eleven weeks after it was 

 infected (Experiment 9, lot 2b). As the cold weather comes on 

 the infection in the houses seems to be much less persistent 

 (Experiment 9, lot 3b). On the whole it must be taken that 

 under normal conditions we must expect material to remain infective 

 for at least about three months — it may be shorter lived than 

 this under some c'onditions but it is not safe to build on that. 

 Unfortunately this period is just long enough as a rule to carry 

 on infection from one bund to the next, so that the necessity of 

 devising some method of protecting worms from infection, by 

 disinfection or otherwise, is necessary in India. In France it -is 

 now recognized, as indeed Pasteur pointed out long ago, that the 

 long interval between the rearing periods of the univoltine races 

 makes disinfection for pebrine more or less unnecessary. Unfor- 

 tunately the bunds of the multivoltine worms reared in India 

 follow each other so closely that we cannot afford to neglect all 

 precautions. If, however, a district that was heavily infected with 

 ■pebrine could be given a six months' rest from rearing, that would 

 probably be more effective than any disinfection. Unfortunately 

 it would hardly be possible to do this. In Kashmir the rearers' 

 houses are never disinfected but pebrine is of no importance 

 rthere— univoltine worms are used. 



Methods of protecting worms from infection. If un- 

 examined seed is used nothing will avail — it would hardly be worth 

 while to bother trying any disinfection or other preventative measures 

 — but if good seed is used it is only right to give it every possible 

 chance and try to eliminate every outside source of infection, how- 

 ever slight it may be, in every possible fashion. There are several 

 different methods by which one may attempt to protect worms from 

 infection. These fall into three main divisions : — 



1. Direct protection from dust containing spores falling on the 

 rearing trays and the worms thereon. 



2. Destruction of the spores in the rearing house by germicides. 



3. Increasing the natural resistance of the worms. 



