802 PROCEEDINGS OF THE THIRD ENTOMOLOGICAL MEETING 



strong by the cross. Vigour may be imparted to a weak race if it is- 

 crossed with a strong one and vice versa. Desirable qualities are imparted 

 to a weak race by crossing it with races possessing the qualities desired. 

 'We have produced about ten multivoltine hybrid races. The yield 

 of silk of some of them is about li times more than that of the multi- 

 voltine races of Bengal. Our object is to produce two types of multi- 

 voltine hybrid races having similarity in size, shape and colour, which' 

 would suit a particular climate. When these two types breed true, 

 their eggs or the eggs of the reciprocal cross can be profitably reared 

 if the resulting hybrid keeps the multivoltine characteristics of the 

 races. In this w^ay only we can infuse new blood and vigour whenever 

 we like. It remains to be seen whether the hybrid races can be established 

 without degeneration. 



If univoltine races are to be reared they should be annually im- 

 ported and the j^rogeny should be combined with the Bengal Borofolii 

 race which has been acclimatized there. Univoltine races of Japan and 

 China, their crossbreds with the Boropolu race and bivoltine races of 

 Japan stand the climate better and hatch more regularly, although 

 the yields of silk of these races are inferior to that of France and Italy. 



Superior cocoons are obtained in all seasons by a cross between (1) 

 a univoltine male, or (2) a male of a cross between a univoltine male 

 and multivoltine female, or (3) a male of successive generations of this 

 cross, and a multivoltine female. The crossing will have to be efEected 

 in each generation as. the eggs of the second generation of this cross will 

 turn univoltine. These univoltine eggs should be sent to cold storage 

 for rearing in spring or in October or November wherever possible. 

 If univoltine eggs are not required then the female cocoons of the hybrid 

 can be rejected by the help of a balance available in France and used 

 for reeling. 



Of all the indigenous races, the Mysore race is the best as far as the 

 yield of silk fs concerned. The Nistari race should be reared in April 

 or May, the Mysore race from July to October and univoltine races 

 from October to March. We do not advise to rear the hybrid races 

 now on a large scale although there is a demand for the eggs of these 

 races. The best test for the suitability of a race in a particular place is 

 by rearing it in the same place. The Mysore race is more susceptible 

 to diseases than the Nistari race. Indigenous races are more hardy and 

 can stand diseases better than the foreign univoltine races. An infusion 

 of univoltine blood in the indigenous races makes the latter less hardy. 

 We do not know^ whether they would be more hardy when they have 

 been acclimatized to the climatic conditions of India for some time. 

 We have produced multivoltine hybrid races by the infusion of uuivol- 



