HOME-GROWN SILKWORM-GUT 203 



process, the worm does not break the thread to form 

 a means of egress at the front of the cocoon, as the 

 cecropia does; hence the long thread may be reeled 

 off, and might furnish a valuable fiber. The film 

 when thus unwound from the cocoon has a beautiful 

 silver tint, and is surprisingly strong for its size. 



The caterpillar reaches an extreme length of three 

 inches or little more, and it is plumper for its length 

 than the cecropia. The general color is blue-green 

 on the back and yellow-green on the sides. Yellow 

 tubercles are found on the back and sides, arranged 

 in lines. 



A caterpillar much resembling polyphemus is luna 

 (Actias luna) . The line on the anal plate is yellow, 

 instead of brown, and the worm is of a different 

 shade of green; and thus may be readily distin- 

 guished. It spins a thinner cocoon, and probably 

 has little value as a gut-producer. 



Among the smallest of this class of the moths is 

 the Callosamia promethea, whose method of attach- 

 ing its cocoon distinguishes this phase of its exist- 

 ence from the preceding varieties. A handle, like 

 an umbrella's, securely holds the cocoon to the twig 

 or leaf-stem. This is a pretty little moth, but the 

 results of my experiments with it go to show that as 

 a producer of gut it is a failure, the strand being 

 small, short, and weak. 



An imported variety, from China, is the cynthia 

 or ailanthus silkworm. Its cocoon and method of 



