INSTITUTE, PUSA, FOR 1916-17 111 



connected with its solution would be greatly reduced in 

 number. 



V. Pebrine. 



Further work on this subject was carried out and a 

 Bulletin describing a revised method of examination of 

 moths was published. 



The rearing of worms (mulberry) was continued under 

 controlled conditions with a view to determining the follow- 

 ing points in connection with the incidence of pebrine. 



Some 90 lots were reared under controlled conditions 

 besides many larger broods in a separate kutcha house. 



Hereditary infection. Broods were reared through- 

 out the year to check the value of the improved method of 

 seed selection and to compare it with the one which has 

 been unsuccessfully used in Bengal during the past ten 

 years. The results of the experiments confirmed the pre- 

 vious conclusion that many cases of pebrine in the moth 

 may escape detection by the ordinary method, which would 

 not do so if examined by the revised one. 



Further confirmation was also obtained of the conclu- 

 sion that a considerable percentage of pebrinized seed may 

 produce worms which can be successfully carried through 

 to the cocoon stage if afforded sufficient space and suitable 

 food, whereas comparatively unfavourable conditions of 

 life such as are frequently found in rearing houses as a 

 consequence of ignorance or carelessness, would have 

 ensured their failure to spin. Such worms, however, can- 

 not be used for seed production, the resistance to the dis- 

 ease consequent upon the favourable conditions of life 

 seldom being sufficient to do more than prevent the rapid 

 multiplication and spread of the parasite in the body of 

 its host which characterizes the disease in less suitable sur- 

 roundings. 



One of the inherent difficulties of this work is the un- 

 avoidable length of time required for the experiments; this 

 is due to the impossibility of ascertaining either the success 

 of an artificial infection, or even whether the vitality of 

 the pebrine parasite has been affected by treatment, until 



