RESOURCES OP AMERICA, SILK, ETC. 407 



The vital functions of the silk-worm are accelerated by warmth, 

 and the time occupied in passing through the various mutations is 

 hastened, not only by the increased temperature, but materially 

 by the degree of attention which is bestowed on the insects. In 

 Madras, according to Dr. Anderson, and where the climate is very 

 warm, the silk-worm passes through all its evolutions in twenty-two 

 days. Here, then, is not only a saving in regard to time and labor, 

 but a great and very important saving also in regard to food. 



The cocoon is usually an inch and a third in length, of an oval 

 form ; the color yellow, or straw, or pure white. The outer cover- 

 ing is like finest wool, and is called fios, and is easily detached ; this 

 being removed, the end of a thread is discovered, of extreme fine- 

 ness. 



After an interval of from fifteen to twenty days' repose, the moth 

 ejects from its mouth a liquor, which moistens the gum and dissolves 

 tiie adhesiveness of the texture of the ball ; and by frequent motions 

 of its head, it loosens and forces aside the filaments, without sunder- 

 ing a single silken thread, until it reappears, transformed to a large 

 butterfly, of a grayish white color, with four wings, two eyes, and 

 two black, feathery horns or plumes. Unshrouded, in this its last 

 and perfect form, both male and female, they come forth to the light 

 of day : from this time they take no visible food to the day of their 

 death. 



They commence laying their eggs in twenty-four or thirty-six 

 hours after leaving the cocoon. Each female usually lays four hun- 

 dred eggs, which firmly adhere to the paper, on which they are ar- 

 ranged in a handsome and circular form. In a few days after, their 

 multifarious labors being ended, the insect dies. 



The silk-worm remains in the chrysalis state a length of time cor- 

 responding with the temperature of the climate. In England they 

 remain 30 days; in France, 21 ; in Spain and Italy, 18 or 20; in 

 the United States, about the same ; and in India, but 11 days. 



A si!k-\vorm sometimes measures more than three inches in its 

 reatest length ; but few attain to dimensions so large. If the 

 jngitudinal dimensions of an insect which attains to 40 lines be 

 compared during the different ages, and their length at the period 

 of hatching being unity, or 1, their length at the end of the first 

 age will be 4 ; at the end of the second age, ; at the end of the 

 third age, 12; at the end of the fourth ao-e, 20; at the end of the 

 fifth age, 40. 



The silk-worm, like other caterpillars, is a cold-blooded insect, its 

 temperature that of the atmosphere in which it breathes. Sudden 

 changes from cold to heat are highly injurious ; yet it has been 

 found that the silk-worm is capable of enduring a great degree of 

 heat, if uniformly maintained. Such a degree they must at times 

 endure in their own native forests, not only of light, but also of heat, 

 with no shelter from the scorching sun but the shadow of a leaf. 

 Yet in no case is a due degree of warmth more needful, than while 

 the insect is forming the cocoon. If, at any time while they are 

 performing this most important labor, they are permitted to suffer 

 from cold, they cease from their labors, and remain inactive, or move 

 but slowly, as may be discerned while the cocoons are yet trans- 

 parent. It has been proved, on dissection of the silk-worms which_ 

 thus suffer and become torpid through cold, that the glutinous mat-' 



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