81 C 175 X 



with attention, because the voracity of the silkworm abates towards 

 evening; anc' many worms show, by rearing their heads, and not eat- 

 ing, that they are approaching the period of torpor, and some already 

 are become torpid. The strips should continue to be widened, so that 

 at least four-fifths of the hurdle should be covered. 



Fourth day of the second age. 



(Ninth of the rearing of the silkworm.) 



This day only nine pounds of picked leaves, chopped small, will be 

 required. The silkworms sink into torpor, and the next day they 

 will have cast their skins, and will be roused, and thus will the second 

 age be accomplished. If, between the moultings, any worms should 

 appear sick, and cease to eat, they must be removed to another room 

 where the air is pure, and a little warmer than that they have left, put 

 on clean paper, and some fresh leaves chopped fine given to them. 



The alterations which the silk worm undergoes, besides that of the 

 moulting in the second age, are as follows: 



Their color becomes of a light gray; the hair is hardly to be per^ 

 ceived by the naked eye, and becomes shorter; the muzzle, which 

 in the first age was very black, hard, and scaly, became immediately^, 

 upon moulting, white and soft, but afterwards again grew black, shin- 

 ing, and shelly, as before. As the insect grows older, at each moult- 

 ing its muzzle hardens, because it needs to saw and bite larger and 

 older leaves. 



There appear now two curved lines, opposite each other, upon the 

 silkworm's back. 



The length of the silkworms, in the first age, was rather less than 

 four lines; in the second age, of rather more than six lines. 



In four days it has increased its average weight fourfold : when is- 

 suing from the first moulting, 3,240 silkworms formed one ounce: at 

 this period, 610 will form this weight. 



As the insect grows, it breathes more freely, its excrements are 

 more plentiful, which, as the number of hurdles also increase in the 

 laboratory, makes it necessary that the interior air should be more re- 

 novated; and to efiect this, the ventilator in the floor, and the aperture 

 made in the door, should be opened. 



Should there be no wind, and the external air be cold, the ventilator 

 may be left open until the thermometer has lost a degree, or, indeed, 

 two complete degrees. Then all should be closed ; the temperature 

 again rises, and thus has the interior air been thoroughly renewed and 

 purified.* 



* Great care must be taken in pickiag and sorting the leaves for the worms of the 

 first ages, such as picking off all the twigs and stalks of the leaves, and to cleai- them, 

 as much as possible, from all useless parts. This operation is most essential in the 

 two first ages. The sorting and picking is of importance, inasmuch as it enables us 

 to put 15 or 20 per cent, less substance upon the trays, or frames, than wduld othir 

 ^"ise be done, and which the worms do not eat. 

 11 



