166 TEXTILE FIBRES. 



This species of silkworm turned out a failure. 



J The Lepidoptera (or scale-winged insects) is the group to which the 

 silkworm belongs, and Bombyx is the generic name. The principal species 

 for the production of silk is the Bombyx mori. 



There are several species of silk-moth in India that feed on the 

 mulberry. These include Bombyx textor, known also as the Coropooloo, 

 which produces a soft, silky cocoon. B. sinemis is the Chinese silkworm, 

 which produces a soft cocoon. Another is known as the Burmese silk- 

 worm, or Bombyx Arracanensis. 



The Chinese Ttissur silkworm feeds principally on the leaves of 

 species of oak (Quercus). Anther&a mylitta builds a peculiar hard- 

 looking cocoon ; it hangs supended from a twig by a terminal appendage 

 of the outside of the cocoon. The cocoon is oblong in shape, with 

 wrinkled and striated markings, and has a silvery grey colour. Nearly 

 all the Tussur silk of commerce is from this species of silkworm. 



The Japanese silkworm is the Antherxa yama-mai. This also feeds 

 upon the foliage of the oak when obtainable. Unfortunately the Yama- 

 mai silk-moth goes through its larval or feeding stage at a time when 

 the oak tree is almost destitute of foliage, or while the leaves are not 

 sufficiently matured for the silkworm to feed upon. 



Other silkworms which produce wild silk are the caterpillars of the 

 Atlas moth Attacus atlas, which is almost restricted to India, China, 

 and Java ; Attacus cynthia, reared as a domestic species in China, 

 whose larva feeds upon the leaves of the "Tree of Heaven," Ailanthus 

 glandulosa, and Attacus ricini, whose larva feeds upon the segmental 

 lobed leaves of the Castor Oil plant (Ricinus communis), The cocoons 

 vary in colour from orange red to white. 



The weight of the individual cocoons varies from 16 to 50 grains. 

 The outer protective part of the cocoon is of a hard gummy substance ; 

 it is termed the husk or Jcnub. 



The silk fibres are made up of two outer transparent or double parts, 

 termed the bave. It is the reelable portion, and in some cocoons it will 

 reach 700 yards, in others 4000, and in some only 300 yards. 



According to Sir Thomas Wardle the bave portion of the fibre 

 measures on an average -$^ to T ^V^ inch at the thinnest, and from T J^ to 

 ^J^ inch at the thickest part. In some specimens the middle length is 

 one-third thicker, stronger, and more elastic than the ends. 



The central part of a silk fibre is the core or fibroin. The fibre is 

 coated with albumen and a waxy colouring matter. This fibroin has 

 the appearance of pure silk. It is brilliant, soft, and of a pearly lustre. 

 Its chemical formula is C 15 H 23 N 5 O, ; . The coating of the fibre is 

 gelatinous and gummy ; its formula is C 15 H 05 N 5 O 8 . 



