344 TROPICAL AGRICULTURE 



SILK 



Among the useful insects which occur in tropical countries 

 it may be worth while briefly to consider the silkworm, bees, 

 the lac insect, and the cochineal insect. According to Chinese 

 records, the silk industry originated in China about 2600 B. C. 

 From China it passed over to Korea, Japan, Constantinople 

 (550 A. D.), and then throughout the countries where silk- 

 worms are now raised. Both Chinese and Japanese use enor- 

 mous quantities of silk and statistics on total production are 

 not very reliable. In 1908, China produced 29,000,000 pounds 

 of silk, Japan 25,000,000, India 10,000,000, the Levant, 5,- 

 600,000, and Indo-China 2,400,000. The total world produc- 

 tion for that year was about 77,000,000 pounds. 



The total exports of silk from the producing countries is 

 now about 60,000,000 pounds, of which Japan exports 26,- 

 000,000, China 19,000,000, Italy 7,800,000, the Levant 5,000,- 

 ooo, British India 220,000 and Indo-China, 33,000. 



The United States imports about 25,000,000 pounds of silk 

 annually. There is no likelihood, however, of the establish- 

 ment of a commercial silk industry in the United States for 

 the reason that hand labor is too expensive. The immense 

 amount of hand work in silk culture makes cheap labor a neces- 

 sity. Commercial silk production must therefore apparently be 

 confined to regions where cheap labor is available, particularly 

 China, Japan, Italy, and the Levant. 



The silk moth lays 300 to 700 eggs and the life cycle occu- 

 pies about 65 days for each generation. About 2,200 pounds 

 of mulberry leaves are required for the growth of the worms 

 which hatch from one ounce of eggs. This of itself indicates 

 the enormous amount of hand work connected with the in- 

 dustry. Silk cocoons are gathered about 7 to 10 days after 

 the beginning of the spinning. The length of the silk thread 

 in a cocoon varies from 900 to 1,600 yards and cocoons com- 

 monly weigh at the rate of 155 to 320 to the pound. The 



