BAG-WORMS. 



lers and seldom leave the tree on which they were born, 

 but when full grown they become quite restless, and it is 

 this time that they do all their travelling, dropping on to 

 persons by their silken threads and crossing the sidewalks 

 in all directions. A wise instinct urges them to do this, 

 for did they remain on one tree, they would soon multiply 

 beyond the power of that tree to sustain them and would 

 in consequence become extinct. When they have lost 

 their migratory desires, they fasten their bags very securely 

 by a strong band of silk to the twigs of the tree on which 

 they happen to be. A strange instinct leads them to thus 

 fasten their cocoons to the twigs only of the trees they 

 inhabit, so that these cocoons will remain secure through 

 the winter, and not to the leaf-stalk where they would be 

 blown down with the leaf. After thus fastening their 

 bags, they line them with a good thickness of the same 

 material, and resting awhile from their labors, at last 

 cast their skins and become chrysalids. Hitherto the 

 worms had all been alike, but now the sexes are distinguish- 

 able, the male chrysalis being but half the size of the female 

 chrysalis. Three weeks afterwards [late August or early 

 September] a still greater change takes place, the sexes 

 differentiating still more. The male chrysalis works 

 himself down to the end of his bag and, hanging half- 

 way out, the skin bursts and the moth with a black body 

 and glassy wings escapes, and when his wings are dry, 

 soars through the air to seek his mate. She never leaves 

 her case, but issues from her chrysalis in the shape of an 

 abortive, footless, and wingless affair and after copulat- 

 ing, works herself back into the chrysalis skin, fills its upper 

 but posterior end with eggs and stops up the other end 

 with what little there is left of her body when she gets 

 through." 



Oiketicus abboti of the Southern States places short 

 pieces of twigs across the bag, making sort of a log cabin. 



The larvae of the small family Lacosomidae also make 

 cases of leaves and silk. These "bags" are rather widely 

 open at both ends. They are not usually common, but 

 are to be looked for on oak. 



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