27 



spoiled. They are then spread out in -i-inch laj^ers, on clean shelves, 

 in an aiiy, dry room, not exposed to sunlight, and ver}^ carefully 

 guarded from rats, mice, and insects. The defective and discolored 

 ones are put in a separate room. 



The thread of a cocoon is continuous with that of the web, and 

 diminishes in diameter within. Its length varies from 1,200 yards to 

 1,600 yards, and its value accordingl3\ 

 Different races, sexes, and conditions 

 of rearing often produce notable dif- 

 ferences in weight of cocoons. Thus 

 the weight may varj" from 155 to 320 

 cocoons to the pound (340 to 700 to the 

 kilogram). 



Often two or more worms are in- 

 closed in the same cocoon. Cocoons 

 formed from such collaboration are 

 larger than single ones, irregular in 

 form, and cottony in texture. They can not be unreeled, and conse- 

 quently are far less valuable than single ones. 



The proportion of silk in a cocoon varies according to the race 

 and the regime to which the worm has been subjected. The average 

 normal cocoon at the time it is sold is thus composed: 



Fig. 12.— Device for removing floss from 

 cocoons. (Redrawn from Nenci.) 



Per cent. 

 fi8 2 



Water 



Silk - 14. 3 



Web and veil 7 



Chrysalis 16. 8 



If the cocoons are not sold as soon as gathered, the chrysalides 

 should be killed without delay unless they are to be reserved for 

 reproduction. Otherwise the moths may pierce the cocoons, thus 

 rendering them unfit to be reeled. 



The chrysalides are usually killed either by heat or suffocation. 

 The means most commonly employed are (1) the heat of the sun; (2) 

 hot dry air in a stove; (3) hot humid air in a stove; (4) steam; (5) oil 

 of turpentine; (6) carbon bisulphid or some other gas. Probably the 

 best of these means are steam at a temperature not above 212"^ F. 

 applied without pressure, or hot damp air at a temperature of 196'^ F. 



The killing of the chrysalides is an important operation and one 

 requiring care and judgment. If some are left alive, the moths will 

 issue, thus rendering the cocoons of little value. On the other hand, 

 if the operation is continued too long, the silk may be injured. The 

 best methods are those in which ttie heat is carefuU}^ controlled and 

 excessive dryness is avoided. 



The following is a very simple and easy way to destroy the chr3'sa- 

 lides b}' the use of steam: 



Place a cauldron of water on a stove. When boiling begins set over the cauldron 

 a white hollow wooden cylinder, about 3 feet high and 2 feet in diameter, with 



165 



