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The common name, bag worm, is derived from the fact that the 

 larva is sheltered by a bag, basket or case, which it carries about as 

 a shelter and in which it undergoes its transformations. These bags 

 are often prominent objects on leafless trees and shrubs in winter, 

 and, when closely examined, two distinct sizes may be noted. The 

 smaller will be found generally empty, or with the remnants of a pupa 

 shell only, while the larger will be found to be usually filled with a 

 yellowish, powdery mass. If this larger bag is carefully cut open, 

 we will find that it, too, contains the shell of a pupa; but filled 

 with numerous small yellowish-white eggs, surrounded by a delicate, 

 fawn-colored, silky down. 



Some time in May, small, active caterpillars develop, which, after 

 working out of the parent sac, at once begin to construct a bag or 

 sac of their own. This little sac is made from bits of leaf tissue, 

 fastened together with threads of silk to form a conical case, just large 

 enough to contain the insect. At first it is carried upright ; but as the 

 larva increases in size and adds to the sac it becomes too heavy and 

 is allowed to hang down and fastened to a twig or leaf by threads 

 of silk when the insect is not actually moving. All sorts of fragments 

 are used in making the sac; but whatever may be the outer cover- 

 ing, the inside is always lined with soft silk. 



The young larva is uniformly brown; when fully grown that por- 

 tion of the body covered by the bag is soft, light yellowish in color, 

 while the head and leg-bearing rings, are horny and mottled with 

 dark brown and white. The numerous hooks with which the small 

 fleshy legs in the middle of the body are furnished, enable the larva 

 to cling so tightly to the lining of the bag that it is with difiiculty 

 pulled out. When ready to transform to the pupal stage, the larva 

 is seized with a wandering fit and travels for long distances, to other 

 trees or shrubs, and thus provides for the spread of the species. 

 Sooner or later a suitable place is found, the bags are attached to a 

 twig or other support and the pupa is formed. 



The bags from which the male moths are to issue become rather 

 more than an inch in length, while those wliich are to produce the 

 females reach nearly double that size. In both sexes the pupse rest 

 with their heads downward in the bag. In about three weeks the 

 male works its way to the lower end and half way out of the bag, 

 then its skin bursts and the moth appears — a small creature, with a 



