JOUENAIi OF ENTOMOLOGY AND ZOOLOGY 85 



the anterior end. In cross-section the outer surface of the case is 

 square; the interior is lined with a cylindrical tube of tough silk 

 which is equal in diameter to the inside diameter of the square 

 exterior framework; the spaces between the corners of the square 

 exterior and the silken tube are filled with silk. At the caudal end 

 of the case, Fig. 16^, the tube narrows abruptly, leaving a circular 

 opening about one-half mm. in diameter. At the time of pupation, 

 as already mentioned, the sheet of perforated silk, Fig. 16c, is 

 placed across the anterior end of the case, and a sheet. Fig \6b, is 

 spun about 4 mm. from the caudal end. The case undergoes no 

 other alteration at the time of pupation. So toughly made are these 

 cases that they persist without deterioration from season to season 

 after their occupants have left them. 



