AGRICULTURAL INDUSTRIES. 197 



When it begins to spin, the silkworm chooses a corner, the fork 

 of a twig, or some such retaining-point for its first thread. The 

 breeder assists it in this incUnation, employing various measures to 

 promote the formation of cocoons. One of the simplest and most 

 practical, is to spread rape-stalks over the bed of the caterpillars 

 about to spin, the numerous light branches of which offer them 

 facilities for fastening their first thread. In other places in Japan, 

 small loose fagots of thickly branching brush, as long as the bed is 

 wide, are bound up and laid across it. I observed still another 

 method, quite different from these, at Nagahama, on the Biwa Lake. 

 Little cornets of straw were spread over the bed, which the cater- 

 pillars easily reached and used quite readily for going into the 

 chrysalis state. 



It takes the caterpillar three or four days to change into a chry- 

 salis. Fu'st it makes a loose, ellipsoidal case, and then, supported 

 by this, — meanwhile twisting and bending its body, which is all the 

 time getting shorter, it forms the cocoon. This consists of a single 

 thread, averaging 400 to 500 meters long, and becoming thinner 

 and weaker towards the centre (in the proportion of 3 to 4). The 

 external, loose web, the floss-silk, German FLockseide, Japanese 

 Noshi and Mazuata, French bourre, consists of many thin, and on 

 that account alone much less valuable, threads. A cross-section of 

 a cocoon wall shows, when magnified, from 5 to la layers of silk, 

 adhering tightly or loosely. The thread which forms them was 

 deposited by the caterpillar in continuous backward turns one on 

 another and sticks fast to the one adjoining. If the layers of thread 

 lie close together, the cocoon-wall has the appearance of parchment, 

 with a thickness of scarcely 0*3 mm. Otherwise, the structure is 

 leafy, and rough, like felt, and the wall is i mm. thick. The weights 

 in grammes of floss-silk, firm silk-web, and pupa, bear to each other 

 the following relation, according to Haberland, taking 100 Japanese 

 cocoons of Italian breeding : — 



Floss-silk. Firm silk. Pupa. Together. 



Green-spinners 0*52 i6*oo io8*io I24'52 



White-spinners 0*48 i5"34 io6*20 122*02 



from which it appears that green-spinners have [3*26 per cent, and 

 white spinners 12-69 per cent, of silk in the total weight of the 

 cocoon. 



From seven to nine days after the caterpillars have spun, the 

 cocoons are taken from their resting-places and separated from the 

 floss-silk that surrounds them. The best are chosen for breeding, 

 and the pupae of the remainder are killed by being exposed to the 

 sun, or by steam or heated air. The cocoons are then dried and 

 put away to be wound off, or sold to large factories or reeling-estab- 

 lishments — filandas. A cocoon is well-shaped or normal when it 

 has full walls and a sharply accentuated form, a fine, close web, 

 and firmness, especially at the ends. As a rule they are ellipsoidal, 



