BUTTERFLIES AND MOTHS 333 



worms," are hatched. They are of grayish-white colour, with a few 

 darker spots on the back and a small horn on the last but one of the 

 abdominal somites. "When the caterpillars are full grown they begin to 

 spin a web around themselves amongst brushwood and straw, provided 

 for the purpose by their owners. As the thread emerges from the 

 labium (see white cabbage butterfly) it is glued on to a twig, then to 

 another, and so on, until a loose meshwork is formed, containing the 

 larva in its interior. The insect next twines the threads round itself 

 until they form a dense weft or feltwork, the cocoon, in which the pupa 

 passes its quiescent stage. To an animal living in the natural state this 

 firm and safe dwelling forms an excellent protection against enemies. 

 After two or three weeks the perfected moth casts its pupal skin. Being, 

 like all the Lepidoptera, unprovided with biting jaws, it must use other 

 means for breaking through the pupal envelope. For this purpose it 

 secretes from the mouth a brown acid liquid, which softens and loosens 

 the web, which the moth finally tears by boring and pushing with its 

 head. (The other members of this family construct similar webs, and 

 break them in a like manner.) Hence, in German, moths of this family 

 are called " spinners." 



C. Method of Obtaining the Silk. 



The silkworm-keeper only allows a certain number of moths, as many 

 as may be required for breeding, to escape from the cocoons. The 

 majority are killed by heat, his object being to obtain the continuous 

 thread of silk, over 3,000 feet in length, which would be torn by the moth 

 if it were allowed to escape. The cocoons are therefore placed in hot 

 water and beaten with birch rods. The heat loosens the cement by 

 which the threads are held together, and the separated threads adhere to 

 the twigs of the birch. A certain number of threads (up to twenty) are 

 next twisted into a single thread and wound off. In this way a long 

 silk thread is obtained, which is manufactured into silk yarn, dress 

 materials, etc. 



Other Bombycidae. 



Many members of this family are injurious to man. This specially 

 applies to the larva of the Pine Lappet (Gastropacha pini), which is 

 among the most destructive pests of pine and fir woods on the Continent. 

 One or two specimens have been taken in England, but it is not really a 

 native of the British Isles. The colour of both the caterpillar and moth 

 exactly resembles that of the bark of pine-trees. (The moth, like all the 

 Bombycidae, rests with its wings depressed.) With the advent of frosty 



