62 GENERAL ZOOLOGY 



diurnal in their habits, though by far the larger number fly 

 by night. Most of them spin some kind of cocoon in which 

 they pass the pupal stage. 



We shall first consider the silkworm moths. Of these the 

 best known, as it is economically the most important, is 

 the Chinese silkworm moth (Bom'byx mo'ri). Cultivated in 

 China from very early times, the Chinese jealously guarded 

 the secrets of the manufacture of silk. As the story goes, in 

 the middle of the sixth century two monks brought the 

 eggs to Constantinople by stealth, concealed in a hollow 

 bamboo cane. The cultivation of the silkworm then spread 

 rapidly to those parts of Europe suited to its culture. From 

 1609 to the present day various efforts have been made to 

 introduce silk culture into the United States, the plan of 

 bounties and rewards to stimulate its growth having been 

 tried by the rulers in colonial days, and by several states 

 since the war of 1861-1865. These artificial means have 

 so far not met with great success. In China the caterpillar 

 thrives best on the leaves of the white mulberry, but it has 

 been found to do well on the Osage orange. 



The silk glands extend through the body of the caterpil- 

 lar and open into the mouth. Toward the time of pupation 

 they increase in size and produce about four thousand yards 

 of material, which, on being exposed to the air, hardens and 

 becomes the silk of commerce. As there are two sets of these 

 glands, each silk filament is really double. Within this co- 

 coon of silk the larva casts its caterpillar skin and becomes 

 a pupa. In silk culture the cocoons are placed in an oven to 

 kill the pupae, and the silk is softened by being placed in 

 warm water. Then, by means of a twig moved about among 

 the cocoons, loose ends of several of them are caught, united 

 into one thread, and wound on a reel, which is placed at a 

 distance from the hot water so that the silk may dry. This 

 is the raw silk of commerce. 



