14 



Formerly, through an indiscriminate use of eggs, disease invaded 

 the rearings to such a degree that from 65 to 90 pounds of cocoons 

 was considered a good yield per ounce of eggs. At the present low 

 price of silk such cultures are no longer remunerative, and industrial 

 silk culture now demands the exclusive use of scientifically tested eggs. 



The grainage, or preparation of eggs for market, constitutes a special 

 department of silk culture. In Italy there are over 400 establish- 

 ments which supply eggs to raise the annual silk crop. The poorest 

 peasant, though well skilled in the art of rearing silkworms, would 

 not risk a rearing with eggs which have not been selected and pre- 

 served by experts. 



The eggs of crossed races are best for culture with a view to pro- 

 duction of silk, and here, as much as in the examinations which have 

 been referred to, the knowlege of experts is needed. 



The life of the eggj in those races which have but one generation each 

 year, has three phases, the first lasting about three months, full of 

 activity; the second lasting from about October to the middle of Febru- 

 ary, one of inactivity, in which there are no signs of life; the third from 

 the middle of February to the moment of hatching, in which the vital 

 activity recommences, and the germ begins to organize as soon as the 

 temperature rises a little above 50° F. The measure of the activity 

 of the egg, in this stage, is the measure of its danger, for any sudden 

 change of temperature would injure or destroy the delicate embryo, 

 or cause the larva to be born before its food was ready. To guard 

 against such accidents, eggs must be wintered in a high region or in a 

 refrigerator at a uniform temperature of about 35° F. , from December 

 15, until the mulberry begins to bud or until hatchings are desired. 

 There should always be good ventilation, the air should not be moist, 

 and great care must be taken to keep the eggs out of the reach of mice 

 and insects. 



Natural hatchings are almost always irregular, extending over eight 

 or ten days, thus multiplying the divisions and rendering the rearing 

 difficult and costly; hence, the necessity for artificial incubation. 



Eighteen days before the time decided on for the hatching, spread 

 out the eggs in thin layers in the incubating room or incubator. The 

 temperature should be 55° F. 



From the fourth day on, gradually increase the temperature two 

 degrees in twenty-four hours until 73° F. is reached, when, at this 

 uniform temperature, hatchings will occur in ten days on an average. 

 This period, however, varies from eight to fifteen days, according to 

 race, the cold supported during the winter, the first grade of heat, and 

 the highest during the incubation, and the number of days taken to 

 pass through these two grades of heat; and also according to the 

 humidity. To obtain a good and complete hatching, a slight humidity 



165 



