THE NET-MAKING CADDIS WORM 



square and draw within it twenty-six vertical lines 

 crossed by thirty parallel ones, keeping the interspaces 

 of equal size. He will thus have wellnigh copied the 

 caddis worm's product. 



It is interesting to note that the same peculiarity 

 marks the meshes of the inner section of an orbweaving 

 spider's snare, and doubtless is produced in the same 

 way. When a thread is spun across the series of radiat- 

 ing lines, the cross-line adheres to the radius; and when 

 it is passed to the next radius the pull upon the one just 

 left draws it a little out of line. This gives the meshes 

 the form of rectangles some of whose corners have been 



A MINIATURE FISHING-LODGB 



A basket-like frame to the net of a hydropsychid caddis worm. 



Net one-fourth inoli square 



283 



